TY  - JOUR
A1  - Yang, Xiao Hui
A1  - Jaiser, Frank
A1  - Neher, Dieter
A1  - Lawson, PaDreyia V.
A1  - Brédas, Jean-Luc
A1  - Zojer, Egbert
A1  - Güntner, Roland
A1  - Scanduicci de Freitas, Patricia
A1  - Forster, Michael
A1  - Scherf, Ullrich
T1  - Suppression of the keto-emission in polyfluorene light-emitting diodes : Experiments and models
N2  - The spectral characteristics of polyfluorene (PF)-based light-emitting diodes (LEDs) containing a defined low concentration of either keto-defects or of the polymer poly(9.9-octylfuorene-co-benzothiadiazole) (F8BT) are preseneted. Both types of blend layers were tested in different device configurations with respect to the relative and absolute intensities of green blue emission components. It is shown that blending hole-transporting molecules into the emission layer at low concentration or incorporation of a suitable hole-transport layer reduces the green emission contribution in the electroluminescence (EL) spectrum of the PF:F8BT blend, which is similar to what is observed for the keto- containing PF layer. We conclude that the keto-defects in PF homopolymer layers mainly constitute weakly emissive electron traps, in agreement with the results of quantum-mechanical calculations
Y1  - 2004
SN  - 1616-301X
ER  - 
TY  - JOUR
A1  - Yang, X. H.
A1  - Neher, Dieter
A1  - Hertel, D.
A1  - Daubler, T. K.
T1  - Highly efficient single-layer polymer electrophosphorescent devices
N2  - A commercially available Ir complex has been employed for the preparation of highly efficient (see Figure) single-layer phosphorescent polymer light,emitting diodes by use of appropriate thermal treatment and proper adjustment of the layer composition. These devices exhibit essentially no dependence of the driving field on the concentration of the Ir complex, suggesting that the build-up of space-charge in the layer is insignificant
Y1  - 2004
SN  - 0935-9648
ER  - 
TY  - JOUR
A1  - Yang, X. H.
A1  - Neher, Dieter
T1  - Polymer electrophosphorescence devices with high power conversion efficiencies
N2  - We demonstrate efficient single-layer polymer phosphorescent light-emitting devices based on a green-emitting iridium complex and a polymer host co-doped with electron-transporting and hole-transporting molecules. These devices can be operated at relatively low voltages, resulting in a power conversion efficiency of up to 24 lm/W at luminous efficiencies exceeding 30 cd/A. The overall performances of these devices suggest that efficient electrophosphorescent devices with acceptable operating voltages can be achieved in very simple device structures fabricated by spin coating. (C) 2004 American Institute of Physics
Y1  - 2004
SN  - 0003-6951
ER  - 
TY  - JOUR
A1  - Yang, X. H.
A1  - Jaiser, Frank
A1  - Klinger, S
A1  - Neher, Dieter
T1  - Blue polymer electrophosphorescent devices with different electron-transporting oxadiazoles
N2  - We report that the performances of blue polymer electrophosphorescent devices are crucially depending on the choice of the electron transporting material incorporated into the emissive layer. Devices with 1,3-bis[(4-tert- butylphenyl)-1,3,4-oxidiazolyl]phenylene (OXD-7) doped at similar to 40 wt% into a poly(vinylcarbazole) matrix exhibited significantly higher efficiencies than those with 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (PBD), yielding maximum luminous and power efficiency values of 18.2 Cd/A and 8.8 lm/W, respectively. Time resolved photoluminescence measurements revealed a long lifetime phosphorescence component in layers with PBD, which we assign to significant triplet harvesting by this electron-transporting component. (c) 2006 American Institute of Physics
Y1  - 2006
UR  - http://scitation.aip.org/getpdf/servlet/ GetPDFServlet?filetype=pdf&id=APPLAB000088000002021107000001&idtype=cvips&doi=10.1063/1.2162693&prog=normal
U6  - https://doi.org/10.1063/1.2162693
ER  - 
TY  - JOUR
A1  - Xu, Jingsan
A1  - Shalom, Menny
A1  - Piersimoni, Fortunato
A1  - Antonietti, Markus
A1  - Neher, Dieter
A1  - Brenner, Thomas J. K.
T1  - Color-Tunable Photoluminescence and NIR Electroluminescence in Carbon Nitride Thin Films and Light-Emitting Diodes
JF  - Advanced optical materials
Y1  - 2015
U6  - https://doi.org/10.1002/adom.201500019
SN  - 2195-1071
VL  - 3
IS  - 7
SP  - 913
EP  - 917
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Xu, Jingsan
A1  - Brenner, Thomas J. K.
A1  - Chen, Zupeng
A1  - Neher, Dieter
A1  - Antonietti, Markus
A1  - Shalom, Menny
T1  - Upconversion-agent induced improvement of g-C3N4 photocatalyst under visible light
JF  - ACS applied materials & interfaces
N2  - Herein, we report the use of upconversion agents to modify graphite carbon nitride (g-C3N4) by direct thermal condensation of a mixture of ErCl3 center dot 6H(2)O and the supramolecular precursor cyanuric acid-melamine. We show the enhancement of g-C3N4 photoactivity after Er3+ doping by monitoring the photodegradation of Rhodamine B dye under visible light. The contribution of the upconversion agent is demonstrated by measurements using only a red laser. The Er3+ doping alters both the electronic and the chemical properties of g-C3N4. The Er3+ doping reduces emission intensity and lifetime, indicating the formation of new, nonradiative deactivation pathways, probably involving charge-transfer processes.
KW  - metal-free photocatalysis
KW  - upconversion
KW  - carbon nitride
KW  - RhB photodegradation
Y1  - 2014
U6  - https://doi.org/10.1021/am5051263
SN  - 1944-8244
VL  - 6
IS  - 19
SP  - 16481
EP  - 16486
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Xu, Jingsan
A1  - Brenner, Thomas J. K.
A1  - Chabanne, Laurent
A1  - Neher, Dieter
A1  - Antonietti, Markus
A1  - Shalom, Menny
T1  - Liquid-Based growth of polymeric carbon nitride layers and their use in a mesostructured polymer solar cell with V-oc exceeding 1 V
JF  - Journal of the American Chemical Society
N2  - Herein we report a general liquid-mediated pathway for the growth of continuous polymeric carbon nitride (C3N4) thin films. The deposition method consists of the use of supramolecular complexes that transform to the liquid state before direct thermal condensation into C3N4 solid films. The resulting films exhibit continuous porous C3N4 networks on various substrates. Moreover, the optical absorption can be easily tuned to cover the solar spectrum by the insertion of an additional molecule into the starting complex. The strength of the deposition method is demonstrated by the use of the C3N4 layer as the electron acceptor in a polymer solar cell that exhibits a remarkable open-circuit voltage exceeding 1 V. The easy, safe, and direct synthesis of carbon nitride in a continuous layered architecture on different functional substrates opens new possibilities for the fabrication of many energy-related devices.
Y1  - 2014
U6  - https://doi.org/10.1021/ja508329c
SN  - 0002-7863
VL  - 136
IS  - 39
SP  - 13486
EP  - 13489
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Würfel, Uli
A1  - Perdigón-Toro, Lorena
A1  - Kurpiers, Jona
A1  - Wolff, Christian Michael
A1  - Caprioglio, Pietro
A1  - Rech, Jeromy James
A1  - Zhu, Jingshuai
A1  - Zhan, Xiaowei
A1  - You, Wei
A1  - Shoaee, Safa
A1  - Neher, Dieter
A1  - Stolterfoht, Martin
T1  - Recombination between Photogenerated and Electrode-Induced Charges Dominates the Fill Factor Losses in Optimized Organic Solar Cells
JF  - The journal of physical chemistry letters
N2  - Charge extraction in organic solar cells (OSCs) is commonly believed to be limited by bimolecular recombination of photogenerated charges. However, the fill factor of OSCs is usually almost entirely governed by recombination processes that scale with the first order of the light intensity. This linear loss was often interpreted to be a consequence of geminate or trap-assisted recombination. Numerical simulations show that this linear dependence is a direct consequence of the large amount of excess dark charge near the contact. The first-order losses increase with decreasing mobility of minority carriers, and we discuss the impact of several material and device parameters on this loss mechanism. This work highlights that OSCs are especially vulnerable to injected charges as a result of their poor charge transport properties. This implies that dark charges need to be better accounted for when interpreting electro-optical measurements and charge collection based on simple figures of merit.
Y1  - 2019
U6  - https://doi.org/10.1021/acs.jpclett.9b01175
SN  - 1948-7185
VL  - 10
IS  - 12
SP  - 3473
EP  - 3480
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Würfel, Uli
A1  - Neher, Dieter
A1  - Spies, Annika
A1  - Albrecht, Steve
T1  - Impact of charge transport on current-voltage characteristics and power-conversion efficiency of organic solar cells
JF  - Nature Communications
N2  - This work elucidates the impact of charge transport on the photovoltaic properties of organic solar cells. Here we show that the analysis of current-voltage curves of organic solar cells under illumination with the Shockley equation results in values for ideality factor, photo-current and parallel resistance, which lack physical meaning. Drift-diffusion simulations for a wide range of charge-carrier mobilities and illumination intensities reveal significant carrier accumulation caused by poor transport properties, which is not included in the Shockley equation. As a consequence, the separation of the quasi Fermi levels in the organic photoactive layer (internal voltage) differs substantially from the external voltage for almost all conditions. We present a new analytical model, which considers carrier transport explicitly. The model shows excellent agreement with full drift-diffusion simulations over a wide range of mobilities and illumination intensities, making it suitable for realistic efficiency predictions for organic solar cells.
Y1  - 2015
U6  - https://doi.org/10.1038/ncomms7951
SN  - 2041-1723
VL  - 6
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - JOUR
A1  - Wolff, Christian Michael
A1  - Zu, Fengshuo
A1  - Paulke, Andreas
A1  - Perdigón-Toro, Lorena
A1  - Koch, Norbert
A1  - Neher, Dieter
T1  - Reduced Interface-Mediated Recombination for High Open-Circuit Voltages in CH3NH3PbI3 Solar Cells
JF  - Advanced materials
N2  - Perovskite solar cells with all-organic transport layers exhibit efficiencies rivaling their counterparts that employ inorganic transport layers, while avoiding high-temperature processing. Herein, it is investigated how the choice of the fullerene derivative employed in the electron-transporting layer of inverted perovskite cells affects the open-circuit voltage (V-OC). It is shown that nonradiative recombination mediated by the electron-transporting layer is the limiting factor for the V-OC in the cells. By inserting an ultrathin layer of an insulating polymer between the active CH3NH3PbI3 perovskite and the fullerene, an external radiative efficiency of up to 0.3%, a V-OC as high as 1.16 V, and a power conversion efficiency of 19.4% are realized. The results show that the reduction of nonradiative recombination due to charge-blocking at the perovskite/organic interface is more important than proper level alignment in the search for ideal selective contacts toward high V-OC and efficiency.
KW  - electron-transport layers
KW  - nonradiative recombination
KW  - open-circuit voltage
KW  - perovskite solar cells
Y1  - 2017
U6  - https://doi.org/10.1002/adma.201700159
SN  - 0935-9648
SN  - 1521-4095
VL  - 29
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Wilson, J. N.
A1  - Steffen, W.
A1  - McKenzie, T. G.
A1  - Lieser, G.
A1  - Oda, Masao
A1  - Neher, Dieter
A1  - Bunz, Uwe H. F.
T1  - Chiroptcial properties of poly(p-phenyleneethynylene) copolymers in thin films : large g-values
Y1  - 2002
ER  - 
TY  - JOUR
A1  - Warby, Jonathan
A1  - Zu, Fengshuo
A1  - Zeiske, Stefan
A1  - Gutierrez-Partida, Emilio
A1  - Frohloff, Lennart
A1  - Kahmann, Simon
A1  - Frohna, Kyle
A1  - Mosconi, Edoardo
A1  - Radicchi, Eros
A1  - Lang, Felix
A1  - Shah, Sahil
A1  - Pena-Camargo, Francisco
A1  - Hempel, Hannes
A1  - Unold, Thomas
A1  - Koch, Norbert
A1  - Armin, Ardalan
A1  - De Angelis, Filippo
A1  - Stranks, Samuel D.
A1  - Neher, Dieter
A1  - Stolterfoht, Martin
T1  - Understanding performance limiting interfacial recombination in pin Perovskite solar cells
JF  - Advanced energy materials
N2  - Perovskite semiconductors are an attractive option to overcome the limitations of established silicon based photovoltaic (PV) technologies due to their exceptional opto-electronic properties and their successful integration into multijunction cells. However, the performance of single- and multijunction cells is largely limited by significant nonradiative recombination at the perovskite/organic electron transport layer junctions. In this work, the cause of interfacial recombination at the perovskite/C-60 interface is revealed via a combination of photoluminescence, photoelectron spectroscopy, and first-principle numerical simulations. It is found that the most significant contribution to the total C-60-induced recombination loss occurs within the first monolayer of C-60, rather than in the bulk of C-60 or at the perovskite surface. The experiments show that the C-60 molecules act as deep trap states when in direct contact with the perovskite. It is further demonstrated that by reducing the surface coverage of C-60, the radiative efficiency of the bare perovskite layer can be retained. The findings of this work pave the way toward overcoming one of the most critical remaining performance losses in perovskite solar cells.
KW  - C60
KW  - defects
KW  - interface recombination
KW  - loss mechanisms
KW  - perovskites
KW  - solar cells
Y1  - 2022
U6  - https://doi.org/10.1002/aenm.202103567
SN  - 1614-6832
SN  - 1614-6840
VL  - 12
IS  - 12
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Wang, Qiong
A1  - Smith, Joel A.
A1  - Skroblin, Dieter
A1  - Steele, Julian A.
A1  - Wolff, Christian Michael
A1  - Caprioglio, Pietro
A1  - Stolterfoht, Martin
A1  - Köbler, Hans
A1  - Turren-Cruz, Silver-Hamill
A1  - Li, Meng
A1  - Gollwitzer, Christian
A1  - Neher, Dieter
A1  - Abate, Antonio
T1  - Managing phase purities and crystal orientation for high-performance and photostable cesium lead halide perovskite solar cells
JF  - Solar RRL
N2  - Inorganic perovskites with cesium (Cs+) as the cation have great potential as photovoltaic materials if their phase purity and stability can be addressed. Herein, a series of inorganic perovskites is studied, and it is found that the power conversion efficiency of solar cells with compositions CsPbI1.8Br1.2, CsPbI2.0Br1.0, and CsPbI2.2Br0.8 exhibits a high dependence on the initial annealing step that is found to significantly affect the crystallization and texture behavior of the final perovskite film. At its optimized annealing temperature, CsPbI1.8Br1.2 exhibits a pure orthorhombic phase and only one crystal orientation of the (110) plane. Consequently, this allows for the best efficiency of up to 14.6% and the longest operational lifetime, T-S80, of approximate to 300 h, averaged of over six solar cells, during the maximum power point tracking measurement under continuous light illumination and nitrogen atmosphere. This work provides essential progress on the enhancement of photovoltaic performance and stability of CsPbI3 - xBrx perovskite solar cells.
KW  - cesium lead halides
KW  - crystal orientation
KW  - inorganic perovskites
KW  - ISOS-L-1I protocol
KW  - phase purity
KW  - photostability
Y1  - 2020
VL  - 4
IS  - 9
PB  - WILEY-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Wang, Qiong
A1  - Mosconi, Edoardo
A1  - Wolff, Christian Michael
A1  - Li, Junming
A1  - Neher, Dieter
A1  - De Angelis, Filippo
A1  - Suranna, Gian Paolo
A1  - Grisorio, Roberto
A1  - Abate, Antonio
T1  - Rationalizing the molecular design of hole-selective contacts to improve charge extraction in Perovskite solar cells
JF  - dvanced energy materials
N2  - Two new hole selective materials (HSMs) based on dangling methylsulfanyl groups connected to the C-9 position of the fluorene core are synthesized and applied in perovskite solar cells. Being structurally similar to a half of Spiro-OMeTAD molecule, these HSMs (referred as FS and DFS) share similar redox potentials but are endowed with slightly higher hole mobility, due to the planarity and large extension of their structure. Competitive power conversion efficiency (up to 18.6%) is achieved by using the new HSMs in suitable perovskite solar cells. Time-resolved photoluminescence decay measurements and electrochemical impedance spectroscopy show more efficient charge extraction at the HSM/perovskite interface with respect to Spiro-OMeTAD, which is reflected in higher photocurrents exhibited by DFS/FS-integrated perovskite solar cells. Density functional theory simulations reveal that the interactions of methylammonium with methylsulfanyl groups in DFS/FS strengthen their electrostatic attraction with the perovskite surface, providing an additional path for hole extraction compared to the sole presence of methoxy groups in Spiro-OMeTAD. Importantly, the low-cost synthesis of FS makes it significantly attractive for the future commercialization of perovskite solar cells.
KW  - hole extraction
KW  - hole selective materials
KW  - perovskite solar cells
KW  - sulfur
KW  - triple-cation perovskite
Y1  - 2019
U6  - https://doi.org/10.1002/aenm.201900990
SN  - 1614-6832
SN  - 1614-6840
VL  - 9
IS  - 28
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Vollbrecht, Joachim
A1  - Tokmoldin, Nurlan
A1  - Sun, Bowen
A1  - Brus, Viktor V.
A1  - Shoaee, Safa
A1  - Neher, Dieter
T1  - Determination of the charge carrier density in organic solar cells
BT  - a tutorial
JF  - Journal of applied physics
N2  - The increase in the performance of organic solar cells observed over the past few years has reinvigorated the search for a deeper understanding of the loss and extraction processes in this class of device. A detailed knowledge of the density of free charge carriers under different operating conditions and illumination intensities is a prerequisite to quantify the recombination and extraction dynamics. Differential charging techniques are a promising approach to experimentally obtain the charge carrier density under the aforementioned conditions. In particular, the combination of transient photovoltage and photocurrent as well as impedance and capacitance spectroscopy have been successfully used in past studies to determine the charge carrier density of organic solar cells. In this Tutorial, these experimental techniques will be discussed in detail, highlighting fundamental principles, practical considerations, necessary corrections, advantages, drawbacks, and ultimately their limitations. Relevant references introducing more advanced concepts will be provided as well. Therefore, the present Tutorial might act as an introduction and guideline aimed at new prospective users of these techniques as well as a point of reference for more experienced researchers. Published under an exclusive license by AIP Publishing.
KW  - Electrical properties and parameters
KW  - Organic semiconductors
KW  - Solar cells
KW  - Photoconductivity
KW  - Capacitance spectroscopy
Y1  - 2022
U6  - https://doi.org/10.1063/5.0094955
SN  - 0021-8979
SN  - 1089-7550
SN  - 1520-8850
VL  - 131
IS  - 22
PB  - American Institute of Physics
CY  - Melville, NY
ER  - 
TY  - JOUR
A1  - Vandewal, Koen
A1  - Benduhn, Johannes
A1  - Schellhammer, Karl Sebastian
A1  - Vangerven, Tim
A1  - Rückert, Janna E.
A1  - Piersimoni, Fortunato
A1  - Scholz, Reinhard
A1  - Zeika, Olaf
A1  - Fan, Yeli
A1  - Barlow, Stephen
A1  - Neher, Dieter
A1  - Marder, Seth R.
A1  - Manca, Jean
A1  - Spoltore, Donato
A1  - Cuniberti, Gianaurelio
A1  - Ortmann, Frank
T1  - Absorption Tails of Donor
BT  - C-60 Blends Provide Insight into Thermally Activated Charge-Transfer Processes and Polaron Relaxation
JF  - Journal of the American Chemical Society
N2  - In disordered organic semiconductors, the transfer of a rather localized charge carrier from one site to another triggers a deformation of the molecular structure quantified by the intramolecular relaxation energy. A similar structural relaxation occurs upon population of intermolecular charge-transfer (CT) states formed at organic electron donor (D)-acceptor (A) interfaces. Weak CT absorption bands for D A complexes occur at photon energies below the optical gaps of both the donors and the C-60 acceptor as a result of optical transitions from the neutral ground state to the ionic CT state. In this work, we show that temperature-activated intramolecular vibrations of the ground state play a major role in determining the line shape of such CT absorption bands. This allows us to extract values for the relaxation energy related to the geometry change from neutral to ionic CT complexes. Experimental values for the relaxation energies of 20 D:C-60 CT complexes correlate with values calculated within density functional theory. These results provide an experimental method for determining the polaron relaxation energy in solid-state organic D-A blends and show the importance of a reduced relaxation energy, which we introduce to characterize thermally activated CT processes.
Y1  - 2017
U6  - https://doi.org/10.1021/jacs.6b12857
SN  - 0002-7863
VL  - 139
IS  - 4
SP  - 1699
EP  - 1704
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Vandewal, Koen
A1  - Albrecht, Steve
A1  - Hoke, Eric T.
A1  - Graham, Kenneth R.
A1  - Widmer, Johannes
A1  - Douglas, Jessica D.
A1  - Schubert, Marcel
A1  - Mateker, William R.
A1  - Bloking, Jason T.
A1  - Burkhard, George F.
A1  - Sellinger, Alan
A1  - Frechet, Jean M. J.
A1  - Amassian, Aram
A1  - Riede, Moritz K.
A1  - McGehee, Michael D.
A1  - Neher, Dieter
A1  - Salleo, Alberto
T1  - Efficient charge generation by relaxed charge-transfer states at organic interfaces
JF  - Nature materials
N2  - carriers on illumination. Efficient organic solar cells require a high yield for this process, combined with a minimum of energy losses. Here, we investigate the role of the lowest energy emissive interfacial charge-transfer state (CT1) in the charge generation process. We measure the quantum yield and the electric field dependence of charge generation on excitation of the charge-transfer (CT) state manifold viaweakly allowed, low-energy optical transitions. For a wide range of photovoltaic devices based on polymer: fullerene, small-molecule:C-60 and polymer: polymer blends, our study reveals that the internal quantum efficiency (IQE) is essentially independent of whether or not D, A or CT states with an energy higher than that of CT1 are excited. The best materials systems show an IQE higher than 90% without the need for excess electronic or vibrational energy.
Y1  - 2014
U6  - https://doi.org/10.1038/NMAT3807
SN  - 1476-1122
SN  - 1476-4660
VL  - 13
IS  - 1
SP  - 63
EP  - 68
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - JOUR
A1  - Urayama, Kenji
A1  - Tsuji, M.
A1  - Neher, Dieter
T1  - Layer-thinning effects on ferroelectricity and the ferroelectric-to-paraelectric phase transition of vinylidene fluoride-trifluoroethylene copolymer layers
Y1  - 2000
ER  - 
TY  - JOUR
A1  - Urayama, Kenji
A1  - Kircher, Oliver
A1  - Böhmer, Roland
A1  - Neher, Dieter
T1  - Investigations of ferroelectric-to-paraelectric phase transition of vinylidenefluoride trifluoroethylene copolymer thin films by electromechanical interferometry
Y1  - 1999
ER  - 
TY  - JOUR
A1  - Ullbrich, Sascha
A1  - Benduhn, Johannes
A1  - Jia, Xiangkun
A1  - Nikolis, Vasileios C.
A1  - Tvingstedt, Kristofer
A1  - Piersimoni, Fortunato
A1  - Roland, Steffen
A1  - Liu, Yuan
A1  - Wu, Jinhan
A1  - Fischer, Axel
A1  - Neher, Dieter
A1  - Reineke, Sebastian
A1  - Spoltore, Donato
A1  - Vandewal, Koen
T1  - Emissive and charge-generating donor-acceptor interfaces for organic optoelectronics with low voltage losses
JF  - Nature materials
N2  - Intermolecular charge-transfer states at the interface between electron donating (D) and accepting (A) materials are crucial for the operation of organic solar cells but can also be exploited for organic light-emitting diodes(1,2). Non-radiative charge-transfer state decay is dominant in state-of-the-art D-A-based organic solar cells and is responsible for large voltage losses and relatively low power-conversion efficiencies as well as electroluminescence external quantum yields in the 0.01-0.0001% range(3,4). In contrast, the electroluminescence external quantum yield reaches up to 16% in D-A-based organic light-emitting diodes(5-7). Here, we show that proper control of charge-transfer state properties allows simultaneous occurrence of a high photovoltaic and emission quantum yield within a single, visible-light-emitting D-A system. This leads to ultralow-emission turn-on voltages as well as significantly reduced voltage losses upon solar illumination. These results unify the description of the electro-optical properties of charge-transfer states in organic optoelectronic devices and foster the use of organic D-A blends in energy conversion applications involving visible and ultraviolet photons(8-11).
KW  - Electronics, photonics and device physics
KW  - Optoelectronic devices and components
KW  - Photonic devices
KW  - Solar energy and photovoltaic technology
Y1  - 2019
U6  - https://doi.org/10.1038/s41563-019-0324-5
SN  - 1476-1122
SN  - 1476-4660
VL  - 18
IS  - 5
SP  - 459
EP  - 464
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - JOUR
A1  - Turner, Sarah T.
A1  - Pingel, Patrick
A1  - Steyrleuthner, Robert
A1  - Crossland, Edward J. W.
A1  - Ludwigs, Sabine
A1  - Neher, Dieter
T1  - Quantitative analysis of bulk heterojunction films using linear absorption spectroscopy and solar cell performance
JF  - Advanced functional materials
N2  - A fundamental understanding of the relationship between the bulk morphology and device performance is required for the further development of bulk heterojunction organic solar cells. Here, non-optimized (chloroform cast) and nearly optimized (solvent-annealed o-dichlorobenzene cast) P3HT:PCBM blend films treated over a range of annealing temperatures are studied via optical and photovoltaic device measurements. Parameters related to the P3HT aggregate morphology in the blend are obtained through a recently established analytical model developed by F. C. Spano for the absorption of weakly interacting H-aggregates. Thermally induced changes are related to the glass transition range of the blend. In the chloroform prepared devices, the improvement in device efficiency upon annealing within the glass transition range can be attributed to the growth of P3HT aggregates, an overall increase in the percentage of chain crystallinity, and a concurrent increase in the hole mobilities. Films treated above the glass transition range show an increase in efficiency and fill factor not only associated with the change in chain crystallinity, but also with a decrease in the energetic disorder. On the other hand, the properties of the P3HT phase in the solvent-annealed o-dichlorobenzene cast blends are almost indistinguishable from those of the corresponding pristine P3HT layer and are only weakly affected by thermal annealing. Apparently, slow drying of the blend allows the P3HT chains to crystallize into large domains with low degrees of intra- and interchain disorder. This morphology appears to be most favorable for the efficient generation and extraction of charges.
KW  - Organic electronics
KW  - morphology
KW  - solar cells
KW  - mobility
KW  - absorption spectroscopy
Y1  - 2011
U6  - https://doi.org/10.1002/adfm.201101583
SN  - 1616-301X
VL  - 21
IS  - 24
SP  - 4640
EP  - 4652
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Tremel, Kim
A1  - Fischer, Florian S. U.
A1  - Kayunkid, Navaphun
A1  - Di Pietro, Riccardo
A1  - Tkachov, Roman
A1  - Kiriy, Anton
A1  - Neher, Dieter
A1  - Ludwigs, Sabine
A1  - Brinkmann, Martin
T1  - Charge transport anisotropy in highly oriented thin films of the acceptor polymer P(NDI2OD-T2)
JF  - dvanced energy materials
N2  - The nanomorphology of the high mobility polymer poly{[N,N'-bis(2-octyldodecyl)-1,4,5,8-naphthalenedicarboximide-2,6-diyl]-alt-5,5'-(2,2'-bithiophene)} P(NDI2OD-T2) in thin films is explored as a function of different annealing conditions and correlated to optical and electrical properties. While nanofibrils with face-on orientation in form I are obtained directly after spin-coating and annealing below the melt transition temperature, clear evidence of lamellar structures is found after melt-annealing followed by slow cooling to room temperature. Interestingly these structural changes are accompanied by distinct changes in the absorption patterns. Electron diffraction measurements further show clear transitions towards predominant edge-on oriented chains in form II upon melt-annealing. Large-scale alignment with dichroic ratios up to 10 and improved order is achieved by high temperature rubbing and subsequent post-rubbing annealing. These highly oriented morphologies allow anisotropic in-plane charge transport to be probed with top-gate transistors parallel and perpendicular to the polymer chain direction. Mobilities up to 0.1 cm(2) V-1 s(-1) are observed parallel to the polymer chain, which is up to 10 times higher than those perpendicular to the polymer chain.
Y1  - 2014
U6  - https://doi.org/10.1002/aenm.201301659
SN  - 1614-6832
SN  - 1614-6840
VL  - 4
IS  - 10
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Tokmoldin, Nurlan
A1  - Vollbrecht, Joachim
A1  - Hosseini, Seyed Mehrdad
A1  - Sun, Bowen
A1  - Perdigón-Toro, Lorena
A1  - Woo, Han Young
A1  - Zou, Yingping
A1  - Neher, Dieter
A1  - Shoaee, Safa
T1  - Explaining the fill-factor and photocurrent losses of nonfullerene acceptor-based solar cells by probing the long-range charge carrier diffusion and drift lengths
JF  - Advanced energy materials
N2  - Organic solar cells (OSC) nowadays match their inorganic competitors in terms of current production but lag behind with regards to their open-circuit voltage loss and fill-factor, with state-of-the-art OSCs rarely displaying fill-factor of 80% and above. The fill-factor of transport-limited solar cells, including organic photovoltaic devices, is affected by material and device-specific parameters, whose combination is represented in terms of the established figures of merit, such as theta and alpha. Herein, it is demonstrated that these figures of merit are closely related to the long-range carrier drift and diffusion lengths. Further, a simple approach is presented to devise these characteristic lengths using steady-state photoconductance measurements. This yields a straightforward way of determining theta and alpha in complete cells and under operating conditions. This approach is applied to a variety of photovoltaic devices-including the high efficiency nonfullerene acceptor blends-and show that the diffusion length of the free carriers provides a good correlation with the fill-factor. It is, finally, concluded that most state-of-the-art organic solar cells exhibit a sufficiently large drift length to guarantee efficient charge extraction at short circuit, but that they still suffer from too small diffusion lengths of photogenerated carriers limiting their fill factor.
KW  - diffusion length
KW  - drift length
KW  - figure of merit
KW  - lifetime‐ mobility product
KW  - steady‐ state photoconductance
Y1  - 2021
U6  - https://doi.org/10.1002/aenm.202100804
SN  - 1614-6840
VL  - 11
IS  - 22
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Tokmoldin, Nurlan
A1  - Hosseini, Seyed Mehrdad
A1  - Raoufi, Meysam
A1  - Phuong, Le Quang
A1  - Sandberg, Oskar J.
A1  - Guan, Huilan
A1  - Zou, Yingping
A1  - Neher, Dieter
A1  - Shoaee, Safa
T1  - Extraordinarily long diffusion length in PM6:Y6 organic solar cells
JF  - Journal of materials chemistry : A, materials for energy and sustainability
N2  - The PM6:Y6 bulk-heterojunction (BHJ) blend system achieves high short-circuit current (J(SC)) values in thick photovoltaic junctions. Here we analyse these solar cells to understand the observed independence of the short-circuit current upon photoactive layer thickness. We employ a range of optoelectronic measurements and analyses, including Mott-Schottky analysis, CELIV, photoinduced absorption spectroscopy, mobility measurements and simulations, to conclude that, the invariant photocurrent for the devices with different active layer thicknesses is associated with the Y6's diffusion length exceeding 300 nm in case of a 300 nm thick cell. This is despite unintentional doping that occurs in PM6 and the associated space-charge effect, which is expected to be even more profound upon photogeneration. This extraordinarily long diffusion length - which is an order of magnitude larger than typical values for organics - dominates transport in the flat-band region of thick junctions. Our work suggests that the performance of the doped PM6:Y6 organic solar cells resembles that of inorganic devices with diffusion transport playing a pivotal role. Ultimately, this is expected to be a key requirement for the fabrication of efficient, high-photocurrent, thick organic solar cells.
Y1  - 2020
U6  - https://doi.org/10.1039/d0ta03016c
SN  - 2050-7488
SN  - 2050-7496
VL  - 8
IS  - 16
SP  - 7854
EP  - 7860
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Tockhorn, Philipp
A1  - Sutter, Johannes
A1  - Cruz Bournazou, Alexandros
A1  - Wagner, Philipp
A1  - Jäger, Klaus
A1  - Yoo, Danbi
A1  - Lang, Felix
A1  - Grischek, Max
A1  - Li, Bor
A1  - Li, Jinzhao
A1  - Shargaieva, Oleksandra
A1  - Unger, Eva
A1  - Al-Ashouri, Amran
A1  - Köhnen, Eike
A1  - Stolterfoht, Martin
A1  - Neher, Dieter
A1  - Schlatmann, Rutger
A1  - Rech, Bernd
A1  - Stannowski, Bernd
A1  - Albrecht, Steve
A1  - Becker, Christiane
T1  - Nano-optical designs for high-efficiency monolithic perovskite-silicon tandem solar cells
JF  - Nature nanotechnology
N2  - Designing gentle sinusoidal nanotextures enables the realization of high-efficiency perovskite-silicon solar cells <br /> Perovskite-silicon tandem solar cells offer the possibility of overcoming the power conversion efficiency limit of conventional silicon solar cells. Various textured tandem devices have been presented aiming at improved optical performance, but optimizing film growth on surface-textured wafers remains challenging. Here we present perovskite-silicon tandem solar cells with periodic nanotextures that offer various advantages without compromising the material quality of solution-processed perovskite layers. We show a reduction in reflection losses in comparison to planar tandems, with the new devices being less sensitive to deviations from optimum layer thicknesses. The nanotextures also enable a greatly increased fabrication yield from 50% to 95%. Moreover, the open-circuit voltage is improved by 15 mV due to the enhanced optoelectronic properties of the perovskite top cell. Our optically advanced rear reflector with a dielectric buffer layer results in reduced parasitic absorption at near-infrared wavelengths. As a result, we demonstrate a certified power conversion efficiency of 29.80%.
Y1  - 2022
U6  - https://doi.org/10.1038/s41565-022-01228-8
SN  - 1748-3387
SN  - 1748-3395
VL  - 17
IS  - 11
SP  - 1214
EP  - 1221
PB  - Nature Publishing Group
CY  - London [u.a.]
ER  - 
TY  - JOUR
A1  - Tait, Claudia E.
A1  - Reckwitz, Anna
A1  - Arvind, Malavika
A1  - Neher, Dieter
A1  - Bittl, Robert
A1  - Behrends, Jan
T1  - Spin-spin interactions and spin delocalisation in a doped organic semiconductor probed by EPR spectroscopy
JF  - Physical chemistry, chemical physics : PCCP ; a journal of European chemical societies
N2  - The enhancement and control of the electrical conductivity of organic semiconductors is fundamental for their use in optoelectronic applications and can be achieved by molecular doping, which introduces additional charge carriers through electron transfer between a dopant molecule and the organic semiconductor. Here, we use Electron Paramagnetic Resonance (EPR) spectroscopy to characterise the unpaired spins associated with the charges generated by molecular doping of the prototypical organic semiconductor poly(3-hexylthiophene) (P3HT) with 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F(4)TCNQ) and tris(pentafluorophenyl)borane (BCF). The EPR results reveal the P3HT radical cation as the only paramagnetic species in BCF-doped P3HT films and show evidence for increased mobility of the detected spins at high doping concentrations as well as formation of antiferromagnetically coupled spin pairs leading to decreased spin concentrations at low temperatures. The EPR signature for F(4)TCNQ-doped P3HT is found to be determined by spin exchange between P3HT radical cations and F(4)TCNQ radical anions. Results from continuous-wave and pulse EPR measurements suggest the presence of the unpaired spin on P3HT in a multitude of environments, ranging from free P3HT radical cations with similar properties to those observed in BCF-doped P3HT, to pairs of dipolar and exchange-coupled spins on P3HT and the dopant anion. Characterisation of the proton hyperfine interactions by ENDOR allowed quantification of the extent of spin delocalisation and revealed reduced delocalisation in the F(4)TCNQ-doped P3HT films.
Y1  - 2021
U6  - https://doi.org/10.1039/d1cp02133h
SN  - 1463-9076
SN  - 1463-9084
VL  - 23
IS  - 25
SP  - 13827
EP  - 13841
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Sun, Bowen
A1  - Sandberg, Oskar
A1  - Neher, Dieter
A1  - Armin, Ardalan
A1  - Shoaee, Safa
T1  - Wave optics of differential absorption spectroscopy in thick-junction organic solar cells
BT  - optical artifacts and correction strategies
JF  - Physical review applied / The American Physical Society
N2  - Differential absorption spectroscopy techniques serve as powerful techniques to study the excited species in organic solar cells. However, it has always been challenging to employ these techniques for characterizing thick-junction organic solar cells, especially when a reflective top contact is involved. In this work, we present a detailed and systematic study on how a combination of the presence of the interference effect and a nonuniform charge-distribution profile, severely manipulates experimental spectra and the decay dynamics. Furthermore, we provide a practical methodology to correct these optical artifacts in differential absorption spectroscopies. The results and the proposed correction method generally apply to all kinds of differential absorption spectroscopy techniques and various thin-film systems, such as organics, perovskites, kesterites, and two-dimensional materials. Notably, it is found that the shape of differential absorption spectra can be strongly distorted, starting from 150-nm active-layer thickness; this matches the thickness range of thick-junction organic solar cells and most perovskite solar cells and needs to be carefully considered in experiments. In addition, the decay dynamics of differential absorption spectra is found to be disturbed by optical artifacts under certain conditions. With the help of the proposed correction formalism, differential spectra and the decay dynamics can be characterized on the full device of thin-film solar cells in transmission mode and yield accurate and reliable results to provide design rules for further progress.
Y1  - 2022
U6  - https://doi.org/10.1103/PhysRevApplied.17.054016
SN  - 2331-7019
VL  - 17
IS  - 5
PB  - American Physical Society
CY  - College Park
ER  - 
TY  - JOUR
A1  - Stolterfoht, Martin
A1  - Wolff, Christian Michael
A1  - Marquez, Jose A.
A1  - Zhang, Shanshan
A1  - Hages, Charles J.
A1  - Rothhardt, Daniel
A1  - Albrecht, Steve
A1  - Burn, Paul L.
A1  - Meredith, Paul
A1  - Unold, Thomas
A1  - Neher, Dieter
T1  - Visualization and suppression of interfacial recombination for high-efficiency large-area pin perovskite solar cells
JF  - Nature Energy
N2  - The performance of perovskite solar cells is predominantly limited by non-radiative recombination, either through trap-assisted recombination in the absorber layer or via minority carrier recombination at the perovskite/transport layer interfaces. Here, we use transient and absolute photoluminescence imaging to visualize all non-radiative recombination pathways in planar pintype perovskite solar cells with undoped organic charge transport layers. We find significant quasi-Fermi-level splitting losses (135 meV) in the perovskite bulk, whereas interfacial recombination results in an additional free energy loss of 80 meV at each individual interface, which limits the open-circuit voltage (V-oc) of the complete cell to similar to 1.12 V. Inserting ultrathin interlayers between the perovskite and transport layers leads to a substantial reduction of these interfacial losses at both the p and n contacts. Using this knowledge and approach, we demonstrate reproducible dopant-free 1 cm(2) perovskite solar cells surpassing 20% efficiency (19.83% certified) with stabilized power output, a high V-oc (1.17 V) and record fill factor (>81%).
KW  - Energy science and technology
KW  - Solar cells
Y1  - 2018
U6  - https://doi.org/10.1038/s41560-018-0219-8
SN  - 2058-7546
VL  - 3
IS  - 10
SP  - 847
EP  - 854
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - JOUR
A1  - Stolterfoht, Martin
A1  - Wolff, Christian Michael
A1  - Amir, Yohai
A1  - Paulke, Andreas
A1  - Perdigón-Toro, Lorena
A1  - Caprioglio, Pietro
A1  - Neher, Dieter
T1  - Approaching the fill factor Shockley-Queisser limit in stable, dopant-free triple cation perovskite solar cells
JF  - Energy & Environmental Science
N2  - Perovskite solar cells now compete with their inorganic counterparts in terms of power conversion efficiency, not least because of their small open-circuit voltage (V-OC) losses. A key to surpass traditional thin-film solar cells is the fill factor (FF). Therefore, more insights into the physical mechanisms that define the bias dependence of the photocurrent are urgently required. In this work, we studied charge extraction and recombination in efficient triple cation perovskite solar cells with undoped organic electron/hole transport layers (ETL/HTL). Using integral time of flight we identify the transit time through the HTL as the key figure of merit for maximizing the fill factor (FF) and efficiency. Complementarily, intensity dependent photocurrent and V-OC measurements elucidate the role of the HTL on the bias dependence of non-radiative and transport-related loss channels. We show that charge transport losses can be completely avoided under certain conditions, yielding devices with FFs of up to 84%. Optimized cells exhibit power conversion efficiencies of above 20% for 6 mm(2) sized pixels and 18.9% for a device area of 1 cm(2). These are record efficiencies for hybrid perovskite devices with dopant-free transport layers, highlighting the potential of this device technology to avoid charge-transport limitations and to approach the Shockley-Queisser limit.
Y1  - 2017
U6  - https://doi.org/10.1039/c7ee00899f
SN  - 1754-5692
SN  - 1754-5706
VL  - 10
SP  - 1530
EP  - 1539
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Stolterfoht, Martin
A1  - Le Corre, Vincent M.
A1  - Feuerstein, Markus
A1  - Caprioglio, Pietro
A1  - Koster, Lambert Jan Anton
A1  - Neher, Dieter
T1  - Voltage-Dependent Photoluminescence and How It Correlates with the Fill Factor and Open-Circuit Voltage in Perovskite Solar Cells
JF  - Acs energy letters
N2  - Optimizing the photoluminescence (PL) yield of a solar cell has long been recognized as a key principle to maximize the power conversion efficiency. While PL measurements are routinely applied to perovskite films and solar cells under open circuit conditions (V-OC), it remains unclear how the emission depends on the applied voltage. Here, we performed PL(V) measurements on perovskite cells with different hole transport layer thicknesses and doping concentrations, resulting in remarkably different fill factors (FFs). The results reveal that PL(V) mirrors the current-voltage (JV) characteristics in the power-generating regime, which highlights an interesting correlation between radiative and nonradiative recombination losses. In particular, high FF devices show a rapid quenching of PL(V) from open-circuit to the maximum power point. We conclude that, while the PL has to be maximized at V-OC at lower biases < V-OC the PL must be rapidly quenched as charges need to be extracted prior to recombination.
Y1  - 2019
U6  - https://doi.org/10.1021/acsenergylett.9b02262
SN  - 2380-8195
VL  - 4
IS  - 12
SP  - 2887
EP  - 2892
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Stolterfoht, Martin
A1  - Grischek, Max
A1  - Caprioglio, Pietro
A1  - Wolff, Christian Michael
A1  - Gutierrez-Partida, Emilio
A1  - Peña-Camargo, Francisco
A1  - Rothhardt, Daniel
A1  - Zhang, Shanshan
A1  - Raoufi, Meysam
A1  - Wolansky, Jakob
A1  - Abdi-Jalebi, Mojtaba
A1  - Stranks, Samuel D.
A1  - Albrecht, Steve
A1  - Kirchartz, Thomas
A1  - Neher, Dieter
T1  - How to quantify the efficiency potential of neat perovskite films
BT  - Perovskite semiconductors with an implied efficiency exceeding 28%
JF  - Advanced Materials
N2  - Perovskite photovoltaic (PV) cells have demonstrated power conversion efficiencies (PCE) that are close to those of monocrystalline silicon cells; however, in contrast to silicon PV, perovskites are not limited by Auger recombination under 1-sun illumination. Nevertheless, compared to GaAs and monocrystalline silicon PV, perovskite cells have significantly lower fill factors due to a combination of resistive and non-radiative recombination losses. This necessitates a deeper understanding of the underlying loss mechanisms and in particular the ideality factor of the cell. By measuring the intensity dependence of the external open-circuit voltage and the internal quasi-Fermi level splitting (QFLS), the transport resistance-free efficiency of the complete cell as well as the efficiency potential of any neat perovskite film with or without attached transport layers are quantified. Moreover, intensity-dependent QFLS measurements on different perovskite compositions allows for disentangling of the impact of the interfaces and the perovskite surface on the non-radiative fill factor and open-circuit voltage loss. It is found that potassium-passivated triple cation perovskite films stand out by their exceptionally high implied PCEs > 28%, which could be achieved with ideal transport layers. Finally, strategies are presented to reduce both the ideality factor and transport losses to push the efficiency to the thermodynamic limit.
KW  - non-radiative interface recombination
KW  - perovskite solar cells
KW  - photoluminescence
Y1  - 2020
U6  - https://doi.org/10.1002/adma.202000080
SN  - 0935-9648
SN  - 1521-4095
VL  - 32
IS  - 17
SP  - 1
EP  - 10
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Stolterfoht, Martin
A1  - Caprioglio, Pietro
A1  - Wolff, Christian Michael
A1  - Marquez, Jose A.
A1  - Nordmann, Joleik
A1  - Zhang, Shanshan
A1  - Rothhardt, Daniel
A1  - Hörmann, Ulrich
A1  - Amir, Yohai
A1  - Redinger, Alex
A1  - Kegelmann, Lukas
A1  - Zu, Fengshuo
A1  - Albrecht, Steve
A1  - Koch, Norbert
A1  - Kirchartz, Thomas
A1  - Saliba, Michael
A1  - Unold, Thomas
A1  - Neher, Dieter
T1  - The impact of energy alignment and interfacial recombination on the internal and external open-circuit voltage of perovskite solar cells
JF  - Energy & environmental science
N2  - Charge transport layers (CTLs) are key components of diffusion controlled perovskite solar cells, however, they can induce additional non-radiative recombination pathways which limit the open circuit voltage (V-OC) of the cell. In order to realize the full thermodynamic potential of the perovskite absorber, both the electron and hole transport layer (ETL/HTL) need to be as selective as possible. By measuring the photoluminescence yield of perovskite/CTL heterojunctions, we quantify the non-radiative interfacial recombination currents in pin- and nip-type cells including high efficiency devices (21.4%). Our study comprises a wide range of commonly used CTLs, including various hole-transporting polymers, spiro-OMeTAD, metal oxides and fullerenes. We find that all studied CTLs limit the V-OC by inducing an additional non-radiative recombination current that is in most cases substantially larger than the loss in the neat perovskite and that the least-selective interface sets the upper limit for the V-OC of the device. Importantly, the V-OC equals the internal quasi-Fermi level splitting (QFLS) in the absorber layer only in high efficiency cells, while in poor performing devices, the V-OC is substantially lower than the QFLS. Using ultraviolet photoelectron spectroscopy and differential charging capacitance experiments we show that this is due to an energy level mis-alignment at the p-interface. The findings are corroborated by rigorous device simulations which outline important considerations to maximize the V-OC. This work highlights that the challenge to suppress non-radiative recombination losses in perovskite cells on their way to the radiative limit lies in proper energy level alignment and in suppression of defect recombination at the interfaces.
Y1  - 2019
U6  - https://doi.org/10.1039/c9ee02020a
SN  - 1754-5692
SN  - 1754-5706
VL  - 12
IS  - 9
SP  - 2778
EP  - 2788
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Stolterfoht, Martin
A1  - Armin, Ardalan
A1  - Philippa, Bronson
A1  - Neher, Dieter
T1  - The Role of Space Charge Effects on the Competition between Recombination and Extraction in Solar Cells with Low-Mobility Photoactive Layers
JF  - The journal of physical chemistry letters
N2  - The competition between charge extraction and nongeminate recombination critically determines the current-voltage characteristics of organic solar cells (OSCs) and their fill factor. As a measure of this competition, several figures of merit (FOMs) have been put forward; however, the impact of space charge effects has been either neglected, or not specifically addressed. Here we revisit recently reported FOMs and discuss the role of space charge effects on the interplay between recombination and extraction. We find that space charge effects are the primary cause for the onset of recombination in so-called non-Langevin systems, which also depends on the slower carrier mobility and recombination coefficient. The conclusions are supported with numerical calculations and experimental results of 25 different donor/acceptor OSCs with different charge transport parameters, active layer thicknesses or composition ratios. The findings represent a conclusive understanding of bimolecular recombination for drift dominated photocurrents and allow one to minimize these losses for given device parameters.
Y1  - 2016
U6  - https://doi.org/10.1021/acs.jpclett.6b02106
SN  - 1948-7185
VL  - 7
SP  - 4716
EP  - 4721
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Stiller, Burkhard
A1  - Karageorgiev, Peter
A1  - Geue, Thomas
A1  - Morawetz, Knut
A1  - Saphiannikova, Marina
A1  - Mechau, Norman
A1  - Neher, Dieter
T1  - Optically induced mass transport studied by scanning near-field optical- and atomic force microscopy
N2  - Some functionalised thin organic films show a very unusual property, namely the light induced material transport. This effect enables to generate three-dimensional structures on surfaces of azobenzene containing films only caused by special optical excitation. The physical mechanisms underlying this phenomenon have not yet been fully understood, and in addition, the dimensions of structures created in that way are macroscopic because of the optical techniques and the wavelength of the used light. In order to gain deeper insight into the physical fundamentals of this phenomenon and to open possibilities for applications it is necessary to create and study structures not only in a macroscopic but also in nanometer range. We first report about experiments to generate optically induced nano structures even down to 100 nm size. The optical stimulation was therefore made by a Scanning Near-field Optical Microscope (SNOM). Secondly, physical conditions inside optically generated surface relief gratings were studied by measuring mechanical properties with high lateral resolution via pulse force mode and force distance curves of an AFM
Y1  - 2004
SN  - 0204-3467
ER  - 
TY  - JOUR
A1  - Steyrleuthner, Robert
A1  - Schubert, Marcel
A1  - Jaiser, Frank
A1  - Blakesley, James C.
A1  - Chen, Zhihua
A1  - Facchetti, Antonio
A1  - Neher, Dieter
T1  - Bulk electron transport and charge injection in a high mobility n-type semiconducting polymer
N2  - Bulk electron transport in a high mobility n-type polymer is studied by time-of-flight photocurrent measurements and electron-only devices. Bulk electron mobilities of similar to 5 x 10(-3) cm(2)/Vs are obtained. The analysis of the electron currents suggests the presence of an injection barrier for all conventionally used low workfunction cathodes.
Y1  - 2010
UR  - http://www3.interscience.wiley.com/cgi-bin/jhome/10008336
U6  - https://doi.org/10.1002/adma.201000232
SN  - 0935-9648
ER  - 
TY  - JOUR
A1  - Steyrleuthner, Robert
A1  - Schubert, Marcel
A1  - Howard, Ian
A1  - Klaumünzer, Bastian
A1  - Schilling, Kristian
A1  - Chen, Zhihua
A1  - Saalfrank, Peter
A1  - Laquai, Frederic
A1  - Facchetti, Antonio
A1  - Neher, Dieter
T1  - Aggregation in a high-mobility n-type low-bandgap copolymer with implications on semicrystalline morphology
JF  - Journal of the American Chemical Society
N2  - We explore the photophysics of P(NDI2OD-T2), a high-mobility and air-stable n-type donor/acceptor polymer. Detailed steady-state UV-vis and photoluminescence (PL) measurements on solutions of P(NDI2OD-T2) reveal distinct signatures of aggregation. By performing quantum chemical calculations, we can assign these spectral features to unaggregated and stacked polymer chains. NMR measurements independently confirm the aggregation phenomena of P(NDI2OD-T2) in solution. The detailed analysis of the optical spectra shows that aggregation is a two-step process with different types of aggregates, which we confirm by time-dependent PL measurements. Analytical ultracentrifugation measurements suggest that aggregation takes place within the single polymer chain upon coiling. By transferring these results to thin P(NDI2OD-T2) films, we can conclude that film formation is mainly governed by the chain collapse, leading in general to a high aggregate content of similar to 45%. This process also inhibits the formation of amorphous and disordered P(NDI2OD-T2) films.
Y1  - 2012
U6  - https://doi.org/10.1021/ja306844f
SN  - 0002-7863
VL  - 134
IS  - 44
SP  - 18303
EP  - 18317
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Steyrleuthner, Robert
A1  - Di Pietro, Riccardo
A1  - Collins, Brian A.
A1  - Polzer, Frank
A1  - Himmelberger, Scott
A1  - Schubert, Marcel
A1  - Chen, Zhihua
A1  - Zhang, Shiming
A1  - Salleo, Alberto
A1  - Ade, Harald W.
A1  - Facchetti, Antonio
A1  - Neher, Dieter
T1  - The Role of Regioregularity, Crystallinity, and Chain Orientation on Electron Transport in a High-Mobility n-Type Copolymer
JF  - Journal of the American Chemical Society
Y1  - 2014
U6  - https://doi.org/10.1021/ja4118736
SN  - 0002-7863
VL  - 136
IS  - 11
SP  - 4245
EP  - 4256
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Steyrleuthner, Robert
A1  - Bange, Sebastian
A1  - Neher, Dieter
T1  - Reliable electron-only devices and electron transport in n-type polymers
N2  - Current-voltage analysis of single-carrier transport is a popular method for the determination of charge carrier mobilities in organic semiconductors. Although in widespread use for the analysis of hole transport, only a few reports can be found where the method was applied to electron transport. Here, we summarize the experimental difficulties related to the metal electrode leakage currents and nonlinear differential resistance (NDR) effects and explain their origin. We present a modified preparation technique for the metal electrodes and show that it significantly increases the reliability of such measurements. It allows to produce test devices with low leakage currents and without NDR even for thin organic layers. Metal oxides were often discussed as a possible cause of NDR. Our measurements on forcibly oxidized metal electrodes demonstrate that oxide layers are not exclusively responsible for NDR effects. We present electron transport data for two electron-conducting polymers often applied in all-polymer solar cells for a large variety of layer thicknesses and temperatures. The results can be explained by established exponential trapping models.
Y1  - 2009
UR  - http://jap.aip.org/
U6  - https://doi.org/10.1063/1.3086307
SN  - 0021-8979
ER  - 
TY  - JOUR
A1  - Srikhirin, Toemsak
A1  - Laschitsch, Alexander
A1  - Neher, Dieter
A1  - Johannsmann, Diethelm
T1  - Light-induced softening of azobenzene dye-doped polymer films probed with quartz crystal resonators
Y1  - 2000
ER  - 
TY  - JOUR
A1  - Srikhirin, T.
A1  - Cimrova, V.
A1  - Schiewe, B.
A1  - Tzolov, M.
A1  - Hagen, R.
A1  - Kostromine, S.
A1  - Bieringer, Thomas
A1  - Neher, Dieter
T1  - An Investigation of the photoinduced changes of absoprtion of high-performance photoaddressable Polymers
Y1  - 2002
ER  - 
TY  - JOUR
A1  - Sini, Gjergji
A1  - Schubert, Marcel
A1  - Risko, Chad
A1  - Roland, Steffen
A1  - Lee, Olivia P.
A1  - Chen, Zhihua
A1  - Richter, Thomas V.
A1  - Dolfen, Daniel
A1  - Coropceanu, Veaceslav
A1  - Ludwigs, Sabine
A1  - Scherf, Ullrich
A1  - Facchetti, Antonio
A1  - Frechet, Jean M. J.
A1  - Neher, Dieter
T1  - On the Molecular Origin of Charge Separation at the Donor-Acceptor Interface
JF  - Advanced energy materials
N2  - Fullerene-based acceptors have dominated organic solar cells for almost two decades. It is only within the last few years that alternative acceptors rival their dominance, introducing much more flexibility in the optoelectronic properties of these material blends. However, a fundamental physical understanding of the processes that drive charge separation at organic heterojunctions is still missing, but urgently needed to direct further material improvements. Here a combined experimental and theoretical approach is used to understand the intimate mechanisms by which molecular structure contributes to exciton dissociation, charge separation, and charge recombination at the donor-acceptor (D-A) interface. Model systems comprised of polythiophene-based donor and rylene diimide-based acceptor polymers are used and a detailed density functional theory (DFT) investigation is performed. The results point to the roles that geometric deformations and direct-contact intermolecular polarization play in establishing a driving force ( energy gradient) for the optoelectronic processes taking place at the interface. A substantial impact for this driving force is found to stem from polymer deformations at the interface, a finding that can clearly lead to new design approaches in the development of the next generation of conjugated polymers and small molecules.
KW  - donor-acceptor interfaces
KW  - energy gradients
KW  - geometrical deformations
KW  - nonfullerene acceptors
KW  - organic photovoltaics
KW  - photocurrent generation
KW  - polymer solar cells
Y1  - 2018
U6  - https://doi.org/10.1002/aenm.201702232
SN  - 1614-6832
SN  - 1614-6840
VL  - 8
IS  - 12
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Sianova, D.
A1  - Zen, Achmad
A1  - Nothofer, Heinz-Georg
A1  - Asawapirom, Udom
A1  - Scherf, Ullrich
A1  - Hagen, R.
A1  - Bieringer, Thomas
A1  - Kostromine, S.
A1  - Neher, Dieter
T1  - Photoaddressable alignment layers for fluorescent polymers in polarized electroluminescence devices
Y1  - 2002
ER  - 
TY  - JOUR
A1  - Shoaee, Safa
A1  - Armin, Ardalan
A1  - Stolterfoht, Martin
A1  - Hosseini, Seyed Mehrdad
A1  - Kurpiers, Jona
A1  - Neher, Dieter
T1  - Decoding Charge Recombination through Charge Generation in Organic Solar Cells
JF  - Solar RRL
N2  - The in-depth understanding of charge carrier photogeneration and recombination mechanisms in organic solar cells is still an ongoing effort. In donor:acceptor (bulk) heterojunction organic solar cells, charge photogeneration and recombination are inter-related via the kinetics of charge transfer states-being singlet or triplet states. Although high-charge-photogeneration quantum yields are achieved in many donor:acceptor systems, only very few systems show significantly reduced bimolecular recombination relative to the rate of free carrier encounters, in low-mobility systems. This is a serious limitation for the industrialization of organic solar cells, in particular when aiming at thick active layers. Herein, a meta-analysis of the device performance of numerous bulk heterojunction organic solar cells is presented for which field-dependent photogeneration, charge carrier mobility, and fill factor are determined. Herein, a "spin-related factor" that is dependent on the ratio of back electron transfer of the triplet charge transfer (CT) states to the decay rate of the singlet CT states is introduced. It is shown that this factor links the recombination reduction factor to charge-generation efficiency. As a consequence, it is only in the systems with very efficient charge generation and very fast CT dissociation that free carrier recombination is strongly suppressed, regardless of the spin-related factor.
KW  - charge generation
KW  - charge transfers
KW  - non-Langevin recombination
KW  - spin-related factors
Y1  - 2019
U6  - https://doi.org/10.1002/solr.201900184
SN  - 2367-198X
VL  - 3
IS  - 11
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Shivhare, Rishi
A1  - Erdmann, Tim
A1  - Hoermann, Ulrich
A1  - Collado-Fregoso, Elisa
A1  - Zeiske, Stefan
A1  - Benduhn, Johannes
A1  - Ullbrich, Sascha
A1  - Huebner, Rene
A1  - Hambsch, Mike
A1  - Kiriy, Anton
A1  - Voit, Brigitte
A1  - Neher, Dieter
A1  - Vandewal, Koen
A1  - Mannsfeld, Stefan C. B.
T1  - Alkyl Branching Position in Diketopyrrolopyrrole Polymers
BT  - Interplay between Fibrillar Morphology and Crystallinity and Their Effect on Photogeneration and Recombination in Bulk-Heterojunction Solar Cells
JF  - Chemistry of materials : a publication of the American Chemical Society
N2  - Diketopyrrolopyrrole (DPP)-based donor acceptor copolymers have gained a significant amount of research interest in the organic electronics community because of their high charge carrier mobilities in organic field-effect transistors (OFETs) and their ability to harvest near-infrared (NIR) photons in solar cells. In this study, we have synthesized four DPP based donor-acceptor copolymers with variations in the donor unit and the branching point of the solubilizing alkyl chains (at the second or sixth carbon position). Grazing incidence wide-angle X-ray scattering (GIWAXS) results suggest that moving the branching point further away from the polymer backbone increases the tendency for aggregation and yields polymer phases with a higher degree of crystallinity (DoC). The polymers were blended with PC70BM and used as active layers in solar cells. A careful analysis of the energetics of the neat polymer and blend films reveals that the charge-transfer state energy (E-CT) of the blend films lies exceptionally close to the singlet energy of the donor (E-D*), indicating near zero electron transfer losses. The difference between the optical gap and open-circuit voltage (V-OC) is therefore determined to be due to rather high nonradiative 418 +/- 13 mV) and unavoidable radiative voltage losses (approximate to 255 +/- 8 mV). Even though the four materials have similar optical gaps, the short-circuit current density (J(SC)) covers a vast span from 7 to 18 mA cm(-2) for the best performing system. Using photoluminescence (PL) quenching and transient charge extraction techniques, we quantify geminate and nongeminate losses and find that fewer excitons reach the donor-acceptor interface in polymers with further away branching points due to larger aggregate sizes. In these material systems, the photogeneration is therefore mainly limited by exciton harvesting efficiency.
Y1  - 2018
U6  - https://doi.org/10.1021/acs.chemmater.8b02739
SN  - 0897-4756
SN  - 1520-5002
VL  - 30
IS  - 19
SP  - 6801
EP  - 6809
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Shalom, Menny
A1  - Inal, Sahika
A1  - Neher, Dieter
A1  - Antonietti, Markus
T1  - SiO2/carbon nitride composite materials: The role of surfaces for enhanced photocatalysis
JF  - Catalysis today : a serial publication dealing with topical themes in catalysis and related subjects
N2  - The effect of SiO2 nanoparticles on carbon nitride (C3N4) photoactivity performance is described. The composite SiO2-C3N4 materials exhibit a higher activity in the photo degradation of RhB dye. A detailed analysis of the chemical and optical properties of the composite C3N4 materials shows that the photo activity increases with higher SiO2 concentration. We found out that the presence of SiO2 nanoparticles strongly affects the fluorescence intensity of the matrix and life time by the creation of new energy states for charge transfer within the C3N4. Furthermore, the use of SiO2 in the synthesis of C3N4 leads to new morphology with higher surface area which results in another, secondary improvement of C3N4 photoactivity. The effect of different surfaces within C3N4 on its chemical and electronic properties is discussed and a tentative mechanism is proposed. The utilization of SiO2 nanoparticles improves both photophysical and chemical properties of C3N4 and opens new possibilities for further enhancement of C3N4 catalytic properties by the formation of composites with many other materials.
KW  - Carbon nitride
KW  - SiO2 composite material
KW  - Photocatalysis
KW  - RhB degradation
Y1  - 2014
U6  - https://doi.org/10.1016/j.cattod.2013.12.013
SN  - 0920-5861
SN  - 1873-4308
VL  - 225
SP  - 185
EP  - 190
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Shalom, Menny
A1  - Inal, Sahika
A1  - Fettkenhauer, Christian
A1  - Neher, Dieter
A1  - Antonietti, Markus
T1  - Improving Carbon Nitride Photocatalysis by Supramolecular Preorganization of Monomers
JF  - Journal of the American Chemical Society
N2  - Here we report a new and simple synthetic pathway to form ordered, hollow carbon nitride structures, using a cyanuric acid melamine (CM) complex in ethanol as a starting product. A detailed analysis of the optical and photocatalytic properties shows that optimum hollow carbon nitride structures are formed after 8 h of condensation. For this condensation time, we find a significantly reduced fluorescence intensity and lifetime, indicating the formation of new, nonradiative deactivation pathways, probably involving charge-transfer processes. Enhanced charge transfer is seen as well from a drastic increase of the photocatalytic activity in the degradation of rhodamine B dye, which is shown to proceed via photoinduced hole transfer. Moreover, we show that various CM morphologies can be obtained using different solvents, which leads to diverse ordered carbon nitride architectures. In all cases, the CM-C3N4 structures exhibited superior photocatalytic activity compared to the bulk material. The utilization of CM hydrogen-bonded complexes opens new opportunities for the significant improvement of carbon nitride synthesis, structure, and optical properties toward an efficient photoactive material for catalysis.
Y1  - 2013
U6  - https://doi.org/10.1021/ja402521s
SN  - 0002-7863
VL  - 135
IS  - 19
SP  - 7118
EP  - 7121
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Shalom, Menny
A1  - Guttentag, Miguel
A1  - Fettkenhauer, Christian
A1  - Inal, Sahika
A1  - Neher, Dieter
A1  - Llobet, Antoni
A1  - Antonietti, Markus
T1  - In situ formation of heterojunctions in modified graphitic carbon nitride: synthesis and noble metal free photocatalysis
JF  - Chemistry of materials : a publication of the American Chemical Society
N2  - Herein, we report the facile synthesis of an efficient roll-like carbon nitride (C3N4) photocatalyst for hydrogen production using a supramolecular complex composed of cyanuric acid, melamine, and barbituric acid as the starting monomers. Optical and photocatalytic investigations show, along with the known red shift of absorption into the visible region, that the insertion of barbituric acid results in the in situ formation of in-plane heterojuctions, which enhance the charge separation process under illumination. Moreover, platinum as the standard cocatalyst in photocatalysis could be successfully replaced with first row transition metal salts and complexes under retention of 50% of the catalytic activity. Their mode of deposition and interaction with the semiconductor was studied in detail. Utilization of the supramolecular approach opens new opportunities to manipulate the charge transfer process within carbon nitride with respect to the design of a more efficient carbon nitride photocatalyst with controlled morphology and optical properties.
Y1  - 2014
U6  - https://doi.org/10.1021/cm503258z
SN  - 0897-4756
SN  - 1520-5002
VL  - 26
IS  - 19
SP  - 5812
EP  - 5818
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Schwarze, Martin
A1  - Schellhammer, Karl Sebastian
A1  - Ortstein, Katrin
A1  - Benduhn, Johannes
A1  - Gaul, Christopher
A1  - Hinderhofer, Alexander
A1  - Perdigón-Toro, Lorena
A1  - Scholz, Reinhard
A1  - Kublitski, Jonas
A1  - Roland, Steffen
A1  - Lau, Matthias
A1  - Poelking, Carl
A1  - Andrienko, Denis
A1  - Cuniberti, Gianaurelio
A1  - Schreiber, Frank
A1  - Neher, Dieter
A1  - Vandewal, Koen
A1  - Ortmann, Frank
A1  - Leo, Karl
T1  - Impact of molecular quadrupole moments on the energy levels at organic heterojunctions
JF  - Nature Communications
N2  - The functionality of organic semiconductor devices crucially depends on molecular energies, namely the ionisation energy and the electron affinity. Ionisation energy and electron affinity values of thin films are, however, sensitive to film morphology and composition, making their prediction challenging. In a combined experimental and simulation study on zinc-phthalocyanine and its fluorinated derivatives, we show that changes in ionisation energy as a function of molecular orientation in neat films or mixing ratio in blends are proportional to the molecular quadrupole component along the p-p-stacking direction. We apply these findings to organic solar cells and demonstrate how the electrostatic interactions can be tuned to optimise the energy of the charge-transfer state at the donor-acceptor interface and the dissociation barrier for free charge carrier generation. The confirmation of the correlation between interfacial energies and quadrupole moments for other materials indicates its relevance for small molecules and polymers.
Y1  - 2019
U6  - https://doi.org/10.1038/s41467-019-10435-2
SN  - 2041-1723
VL  - 10
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - JOUR
A1  - Schulze, Patricia S. C.
A1  - Bett, Alexander J.
A1  - Bivour, Martin
A1  - Caprioglio, Pietro
A1  - Gerspacher, Fabian M.
A1  - Kabaklı, Özde Ş.
A1  - Richter, Armin
A1  - Stolterfoht, Martin
A1  - Zhang, Qinxin
A1  - Neher, Dieter
A1  - Hermle, Martin
A1  - Hillebrecht, Harald
A1  - Glunz, Stefan W.
A1  - Goldschmidt, Jan Christoph
T1  - 25.1% high-efficiency monolithic perovskite silicon tandem solar cell with a high bandgap perovskite absorber
JF  - Solar RRL
N2  - Monolithic perovskite silicon tandem solar cells can overcome the theoretical efficiency limit of silicon solar cells. This requires an optimum bandgap, high quantum efficiency, and high stability of the perovskite. Herein, a silicon heterojunction bottom cell is combined with a perovskite top cell, with an optimum bandgap of 1.68 eV in planar p-i-n tandem configuration. A methylammonium-free FA(0.75)Cs(0.25)Pb(I0.8Br0.2)(3) perovskite with high Cs content is investigated for improved stability. A 10% molarity increase to 1.1 m of the perovskite precursor solution results in approximate to 75 nm thicker absorber layers and 0.7 mA cm(-2) higher short-circuit current density. With the optimized absorber, tandem devices reach a high fill factor of 80% and up to 25.1% certified efficiency. The unencapsulated tandem device shows an efficiency improvement of 2.3% (absolute) over 5 months, showing the robustness of the absorber against degradation. Moreover, a photoluminescence quantum yield analysis reveals that with adapted charge transport materials and surface passivation, along with improved antireflection measures, the high bandgap perovskite absorber has the potential for 30% tandem efficiency in the near future.
KW  - heterojunction silicon solar cells
KW  - interfaces
KW  - perovskite solar cells
KW  - tandem solar cells
KW  - thin films
Y1  - 2020
VL  - 4
IS  - 7
PB  - John Wiley & Sons, Inc.
CY  - New Jersey
ER  - 
TY  - JOUR
A1  - Schubert, Marcel
A1  - Yin, Chunhong
A1  - Castellani, Mauro
A1  - Bange, Sebastian
A1  - Tam, Teck Lip
A1  - Sellinger, Alan
A1  - Hoerhold, Hans-Heinrich
A1  - Kietzke, Thomas
A1  - Neher, Dieter
T1  - Heterojunction topology versus fill factor correlations in novel hybrid small-molecular/polymeric solar cells
N2  - The authors present organic photovoltaic (OPV) devices comprising a small molecule electron acceptor based on 2- vinyl-4,5-dicyanoimidazole (Vinazene (TM)) and a soluble poly(p-phenylenevinylene) derivative as the electron donor. A strong dependence of the fill factor (FF) and the external quantum efficiency [incident photons converted to electrons (IPCE)] on the heterojunction topology is observed. As-prepared blends provided relatively low FF and IPCE values of 26% and 4.5%, respectively, which are attributed to significant recombination of geminate pairs and free carriers in a highly intermixed blend morphology. Going to an all-solution processed bilayer device, the FF and IPCE dramatically increased to 43% and 27%, respectively. The FF increases further to 57% in devices comprising thermally deposited Vinazene layers where there is virtually no interpenetration at the donor/acceptor interface. This very high FF is comparable to values reported for OPV using fullerenes as the electron acceptor. Furthermore, the rather low electron affinity of Vinazene compound near 3.5 eV enabled a technologically important open circuit voltage (V-oc) of 1.0 V.
Y1  - 2009
UR  - http://jcp.aip.org/
U6  - https://doi.org/10.1063/1.3077007
SN  - 0021-9606
ER  -