55442
2017
2017
eng
1699
1704
6
4
139
article
American Chemical Society
Washington
1
2017-01-24
2017-02-01
--
Absorption Tails of Donor
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.
Journal of the American Chemical Society
C-60 Blends Provide Insight into Thermally Activated Charge-Transfer Processes and Polaron Relaxation
10.1021/jacs.6b12857
28068763
0002-7863
wos:2017
WOS:000393355600055
Vandewal, K (reprint author), Tech Univ Dresden, Dresden Integrated Ctr Appl Phys & Photon Mat IAP, D-01062 Dresden, Germany.; Vandewal, K (reprint author), Tech Univ Dresden, Inst Appl Phys, D-01062 Dresden, Germany.; Ortmann, F (reprint author), Tech Univ Dresden, Inst Mat Sci, Max Bergmann Ctr Biomat, D-01062 Dresden, Germany.; Ortmann, F (reprint author), Tech Univ Dresden, Dresden Ctr Computat Mat Sci, D-01062 Dresden, Germany.; Ortmann, F (reprint author), Tech Univ Dresden, Ctr Adv Elect Dresden Cfaed, D-01062 Dresden, Germany., koen.vandewal@iapp.de; frank.ortmann@tu-dresden.de
2022-07-01T11:34:35+00:00
sword
importub
filename=package.tar
d7fd63417017f9c38637fc66e5266a85
false
true
Koen Vandewal
Johannes Benduhn
Karl Sebastian Schellhammer
Tim Vangerven
Janna E. Rückert
Fortunato Piersimoni
Reinhard Scholz
Olaf Zeika
Yeli Fan
Stephen Barlow
Dieter Neher
Seth R. Marder
Jean Manca
Donato Spoltore
Gianaurelio Cuniberti
Frank Ortmann
Physik
Institut für Physik und Astronomie
Referiert
Import
39169
2015
2015
eng
500
504
5
3
6
article
American Chemical Society
Washington
1
--
--
--
Charge Transfer Absorption and Emission at ZnO/Organic Interfaces
We investigate hybrid charge transfer states (HCTS) at the planar interface between a-NPD and ZnO by spectrally resolved electroluminescence (EL) and external quantum efficiency (EQE) measurements. Radiative decay of HCTSs is proven by distinct emission peaks in the EL spectra of such bilayer devices in the NIR at energies well below the bulk a-NPD or ZnO emission. The EQE spectra display low energy contributions clearly red-shifted with respect to the a-NPD photocurrent and partially overlapping with the EL emission. Tuning of the energy gap between the ZnO conduction band and a-NPD HOMO level (E-int) was achieved by modifying the ZnO surface with self-assembled monolayers based on phosphonic acids. We find a linear dependence of the peak position of the NIR EL on E-int, which unambiguously attributes the origin of this emission to radiative recombination between an electron on the ZnO and a hole on a-NPD. In accordance with this interpretation, we find a strictly linear relation between the open-circuit voltage and the energy of the charge state for such hybrid organicinorganic interfaces.
The journal of physical chemistry letters
10.1021/jz502657z
26261970
1948-7185
wos:2015
WOS:000349137400033
Piersimoni, F (reprint author), Univ Potsdam, Inst Phys & Astron, Karl Liebknecht Str 24-25, D-14476 Potsdam, Germany., fortunato.piersimoni@uni-potsdam.de; koen.vandewal@iapp.de; neher@uni-potsdam.de
German Research Foundation (DFG) [SFB 951, SPP 1355]; German Federal
Ministry for Education and Research (BMBF); Helmholtz-Energie-Allianz
"Hybridphotovoltaik"
Fortunato Piersimoni
Raphael Schlesinger
Johannes Benduhn
Donato Spoltore
Sina Reiter
Ilja Lange
Norbert Koch
Koen Vandewal
Dieter Neher
Institut für Physik und Astronomie
Referiert
49679
2019
2019
eng
459
464
7
5
18
article
Nature Publ. Group
London
1
--
2019-04-01
--
Emissive and charge-generating donor-acceptor interfaces for organic optoelectronics with low voltage losses
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).
Nature materials
10.1038/s41563-019-0324-5
30936478
1476-1122
1476-4660
wos:2019
WOS:000465199900016
Ullbrich, S; Benduhn, J; Vandewal, K (reprint author), Tech Univ Dresden, Dresden Integrated Ctr Appl Phys & Photon Mat IAP, Dresden, Germany.; Ullbrich, S; Benduhn, J; Vandewal, K (reprint author), Tech Univ Dresden, Inst Appl Phys, Dresden, Germany.; Vandewal, K (reprint author), Hasselt Univ, Inst Mat Res IMO IMOMEC, Diepenbeek, Belgium., sascha.ullbrich@tu-dresden.de; johannes.benduhn@tu-dresden.de; koen.vandewal@uhasselt.be
German Federal Ministry for Education and Research (BMBF)Federal Ministry of Education & Research (BMBF) [03IPT602X]; German Research Foundation (DFG)German Research Foundation (DFG) [VA 1035/5-1]; China Scholarship CouncilChina Scholarship Council [201706140127, 201506920047]; DFGGerman Research Foundation (DFG) [382633022, SFB 951, RE 3198/6-1]
2021-02-26T13:25:47+00:00
sword
importub
filename=package.tar
75bea40b9d7d66956af2fd1ebed80269
Ullbrich, Sascha
Benduhn, Johannes
Vandewal, Koen
false
true
Sascha Ullbrich
Johannes Benduhn
Xiangkun Jia
Vasileios C. Nikolis
Kristofer Tvingstedt
Fortunato Piersimoni
Steffen Roland
Yuan Liu
Jinhan Wu
Axel Fischer
Dieter Neher
Sebastian Reineke
Donato Spoltore
Koen Vandewal
eng
uncontrolled
Electronics, photonics and device physics
eng
uncontrolled
Optoelectronic devices and components
eng
uncontrolled
Photonic devices
eng
uncontrolled
Solar energy and photovoltaic technology
Physik
Institut für Physik und Astronomie
Referiert
Import
44693
2016
2016
eng
232
239
8
222
article
Elsevier
Lausanne
1
--
--
--
Fluorine-containing low-energy-gap organic dyes with low voltage losses for organic solar cells
Fluorine-containing donor molecules TFTF, CNTF and PRTF are designed and isomer selectively synthesized for application in vacuum-deposited organic solar cells. These molecules comprise a donor acceptor molecular architecture incorporating thiophene and benzothiadiazole derivatives as the electron-donating and electron-withdrawing moieties, respectively. As opposed to previously reported materials from this class, PRTF can be purified by vacuum sublimation at moderate to high yields because of its higher volatility and better stabilization due to a stronger intramolecular hydrogen bond, as compared to TFTF and CNTF. The UV-vis absorption spectra of the three donors show an intense broadband absorption between 500 nm and 800 nm with, similar positions of their frontier energy levels. The photophysical properties of the three donor molecules are thoroughly tested and optimized in bulk heterojunction solar cells with C-60 as acceptor. PRTF shows the best performance, yielding power conversion efficiencies of up to 3.8%. Moreover, the voltage loss for the PRTF device due to the non radiative recombination of free charge carriers is exceptionally low (0.26 V) as compared to typical values for organic solar cells (>0.34V). (C) 2016 Published by Elsevier B.V.
Synthetic metals : the journal of electronic polymers and electronic molecular materials
10.1016/j.synthmet.2016.10.025
0379-6779
wos2016:2019
WOS:000390823600012
Fang, L (reprint author), Tech Univ Dresden, Inst Angew Photophys, George Bahr Str 1, D-01069 Dresden, Germany., lijia.fang@iapp.de
BMBF [LOTsE/03EK3505D, FKZ 03IPT602X]; Deutsche Forschungsgemeinschaft (DFG) [SFB 951]
importub
2020-03-22T12:19:01+00:00
filename=package.tar
a2c4b977421d32b80f7dd017b213cf14
Lijia Fang
Felix Holzmueller
Tomas Matulaitis
Anne Baasner
Christoph Hauenstein
Johannes Benduhn
Martin Schwarze
Annett Petrich
Fortunato Piersimoni
Reinhard Scholz
Olaf Zeika
Christian Koerner
Dieter Neher
Koen Vandewal
Karl Leo
eng
uncontrolled
(Z)-isomer
eng
uncontrolled
Donor materials
eng
uncontrolled
CH center dot center dot center dot F hydrogen bonds
eng
uncontrolled
Sublimation with good yield
eng
uncontrolled
Low voltage losses
Institut für Physik und Astronomie
Referiert
Import
52432
2018
2018
eng
7
21
8
article
Wiley-VCH
Weinheim
1
2018-04-20
2018-04-20
--
Impact of triplet excited states on the open-circuit voltage of organic solar cells
The best organic solar cells (OSCs) achieve comparable peak external quantum efficiencies and fill factors as conventional photovoltaic devices. However, their voltage losses are much higher, in particular those due to nonradiative recombination. To investigate the possible role of triplet states on the donor or acceptor materials in this process, model systems comprising Zn- and Cu-phthalocyanine (Pc), as well as fluorinated versions of these donors, combined with C-60 as acceptor are studied. Fluorination allows tuning the energy level alignment between the lowest energy triplet state (T-1) and the charge-transfer (CT) state, while the replacement of Zn by Cu as the central metal in the Pcs leads to a largely enhanced spin-orbit coupling. Only in the latter case, a substantial influence of the triplet state on the nonradiative voltage losses is observed. In contrast, it is found that for a large series of typical OSC materials, the relative energy level alignment between T-1 and the CT state does not substantially affect nonradiative voltage losses.
dvanced energy materials
10.1002/aenm.201800451
1614-6832
1614-6840
wos:2018
1800451
WOS:000445666000006
Benduhn, J; Vandewal, K (reprint author), Tech Univ Dresden, Dresden Integrated Ctr Appl Phys & Photon Mat IAP, Nothnitzer Str 61, D-01187 Dresden, Germany.; Benduhn, J; Vandewal, K (reprint author), Tech Univ Dresden, Inst Appl Phys, Nothnitzer Str 61, D-01187 Dresden, Germany., johannes.benduhn@iapp.de; koen.vandewal@uhasselt.be
German Federal Ministry for Education and Research (BMBF) through the InnoProfile project "Organische p-i-n Bauelemente 2.2"Federal Ministry and innovation programme under Marie Sklodowska Curie Grant [722651]; German Research Foundation (DFG)German Research Foundation (DFG) [SFB 951]; Fonds de la Recherche Scientifiques de BelgiqueFonds de la Recherche Scientifique - FNRS [2.5020.11]; Walloon Region [1117545]
2021-10-28T08:13:55+00:00
sword
importub
filename=package.tar
f86d856496f5986875ad43e98857733c
Benduhn, Johannes
false
true
Johannes Benduhn
Fortunato Piersimoni
Giacomo Londi
Anton Kirch
Johannes Widmer
Christian Koerner
David Beljonne
Dieter Neher
Donato Spoltore
Koen Vandewal
eng
uncontrolled
charge-transfer states
eng
uncontrolled
nonradiative voltage losses
eng
uncontrolled
organic solar cells
eng
uncontrolled
triplet excited states
Physik
Institut für Physik und Astronomie
Referiert
Import
Green Open-Access
54827
2017
2017
eng
6
2
article
Nature Publ. Group
London
1
2017-04-10
2017-04-10
--
Intrinsic non-radiative voltage losses in fullerene-based organic solar cells
Organic solar cells demonstrate external quantum efficiencies and fill factors approaching those of conventional photovoltaic technologies. However, as compared with the optical gap of the absorber materials, their open-circuit voltage is much lower, largely due to the presence of significant non-radiative recombination. Here, we study a large data set of published and new material combinations and find that non-radiative voltage losses decrease with increasing charge-transfer-state energies. This observation is explained by considering non-radiative charge-transfer-state decay as electron transfer in the Marcus inverted regime, being facilitated by a common skeletal molecular vibrational mode. Our results suggest an intrinsic link between non-radiative voltage losses and electron-vibration coupling, indicating that these losses are unavoidable. Accordingly, the theoretical upper limit for the power conversion efficiency of single-junction organic solar cells would be reduced to about 25.5% and the optimal optical gap increases to (1.45-1.65) eV, that is, (0.2-0.3) eV higher than for technologies with minimized non-radiative voltage losses.
Nature Energy
10.1038/nenergy.2017.53
2058-7546
wos:2017
17053
WOS:000405744700004
Benduhn, J (reprint author), Tech Univ Dresden, Dresden Integrated Ctr Appl Phys & Photon Mat IAP, Nothnitzer Str 61, D-01187 Dresden, Germany.; Benduhn, J (reprint author), Tech Univ Dresden, Inst Appl Phys, Nothnitzer Str 61, D-01187 Dresden, Germany., johannes.benduhn@iapp.de; ktvingstedt@physik.uni-wuerzburg.de; koen.vandewal@iapp.de
German Federal Ministry for Education and Research (BMBF) through the Framework Programme FP7 under the REA grant [PIEF-GA-2012-327199]; German Research Foundation (DFG) [SFB 951]; Department of the Navy, Office of Naval Research [N00014-14-1-0580]; China Scholarship Council; Christ Church Oxford; UK Engineering and Physical Science Research Council (EPSRC) [EP/L026066/1]
2022-04-19T08:57:34+00:00
sword
importub
filename=package.tar
c51fa139af5f4614ef56660bcc22a57a
Benduhn, Johannes
Tvingstedt, Kristofer
Vandewal, Koen
false
true
Johannes Benduhn
Kristofer Tvingstedt
Fortunato Piersimoni
Sascha Ullbrich
Yeli Fan
Manuel Tropiano
Kathryn A. McGarry
Olaf Zeika
Moritz K. Riede
Christopher J. Douglas
Stephen Barlow
Seth R. Marder
Dieter Neher
Donato Spoltore
Koen Vandewal
Physik
Institut für Physik und Astronomie
Referiert
Import
61173
2022
2022
eng
7
1
5
article
Nature portfolio
Berlin
1
2022-11-29
2022-11-29
--
Open-circuit voltage of organic solar cells
Organic photovoltaics (PV) is an energy-harvesting technology that offers many advantages, such as flexibility, low weight and cost, as well as environmentally benign materials and manufacturing techniques. Despite growth of power conversion efficiencies to around 19 % in the last years, organic PVs still lag behind inorganic PV technologies, mainly due to high losses in open-circuit voltage. Understanding and improving open circuit voltage in organic solar cells is challenging, as it is controlled by the properties of a donor-acceptor interface where the optical excitations are separated into charge carriers. Here, we provide an electrostatic model of a rough donor-acceptor interface and test it experimentally on small molecule PV materials systems. The model provides concise relationships between the open-circuit voltage, photovoltaic gap, charge-transfer state energy, and interfacial morphology. In particular, we show that the electrostatic bias generated across the interface reduces the photovoltaic gap. This negative influence on open-circuit voltage can, however, be circumvented by adjusting the morphology of the donor-acceptor interface.
Organic solar cells, despite their high power conversion efficiencies, suffer from open circuit voltage losses making them less appealing in terms of applications. Here, the authors, supported with experimental data on small molecule photovoltaic cells, relate open circuit voltage to photovoltaic gap, charge-transfer state energy, and donor-acceptor interfacial morphology.
Communications physics
interfacial roughness makes the difference
10.1038/s42005-022-01084-x
2399-3650
outputup:dataSource:WoS:2022
307
WOS:000890286400002
Andrienko, D (corresponding author), Max Planck Inst Polymer Res, Ackermannweg 10, D-55128 Mainz, Germany.; Vandewal, K (corresponding author), Hasselt Univ, Inst Mat Oonderzoek IMOMEC, Diepenbeek, Belgium., koen.vandewal@uhasselt.be; denis.andrienko@mpip-mainz.mpg.de
KAUST Office of Sponsored Research (OSR) [OSR-2018-CARF/CCF-3079,; OSR-CRG2018-3746]; Deutsche Forschungsgemeinschaft (DFG, German Research; Foundation) [SPP 2196, 460766640, TRR 146]; German Federal Ministry of; Education and Research (BMBF) [16ME0012, 01DR20008A]
Vandewal, Koen
2023-10-30T09:07:41+00:00
sword
importub
filename=package.tar
7dec9e711d57591ae02c3bad6d06a2ba
Andrienko, Denis
2921913-9
CC-BY - Namensnennung 4.0 International
Carl Poelking
Johannes Benduhn
Donato Spoltore
Martin Schwarze
Steffen Roland
Fortunato Piersimoni
Dieter Neher
Karl Leo
Koen Vandewal
Denis Andrienko
Physik
Institut für Physik und Astronomie
Referiert
Import
Gold Open-Access
DOAJ gelistet
46182
2017
2017
eng
122
136
8
7
article
Wiley-VCH
Weinheim
1
--
--
--
Reducing Voltage Losses in Cascade Organic Solar Cells while Maintaining High External Quantum Efficiencies
High photon energy losses limit the open-circuit voltage (V-OC) and power conversion efficiency of organic solar cells (OSCs). In this work, an optimization route is presented which increases the V-OC by reducing the interfacial area between donor (D) and acceptor (A). This optimization route concerns a cascade device architecture in which the introduction of discontinuous interlayers between alpha-sexithiophene (alpha-6T) (D) and chloroboron subnaphthalocyanine (SubNc) (A) increases the V-OC of an alpha-6T/SubNc/SubPc fullerene-free cascade OSC from 0.98 V to 1.16 V. This increase of 0.18 V is attributed solely to the suppression of nonradiative recombination at the D-A interface. By accurately measuring the optical gap (E-opt) and the energy of the charge-transfer state (E-CT) of the studied OSC, a detailed analysis of the overall voltage losses is performed. E-opt - qV(OC) losses of 0.58 eV, which are among the lowest observed for OSCs, are obtained. Most importantly, for the V-OC-optimized devices, the low-energy (700 nm) external quantum efficiency (EQE) peak remains high at 79%, despite a minimal driving force for charge separation of less than 10 meV. This work shows that low-voltage losses can be combined with a high EQE in organic photovoltaic devices.
dvanced energy materials
10.1002/aenm.201700855
1614-6832
1614-6840
wos:2017
1700855
WOS:000414711100011
Nikolis, VC; Vandewal, K (reprint author), Tech Univ Dresden, Dresden Integrated Ctr Appl Phys & Photon Mat IAP, Nothnitzer Str 61, D-01187 Dresden, Germany.; Nikolis, VC; Vandewal, K (reprint author), Tech Univ Dresden, Inst Appl Phys, Nothnitzer Str 61, D-01187 Dresden, Germany., vasileios_christos.nikolis@iapp.de; koen.vandewal@iapp.de
German Federal Ministry of Education and Research (BMBF) [FKZ 03IPT602X]
importub
2020-04-19T23:20:01+00:00
filename=package.tar
fc0f58ab2e83eb2a49178e6aa03f60bf
Vasileios C. Nikolis
Johannes Benduhn
Felix Holzmueller
Fortunato Piersimoni
Matthias Lau
Olaf Zeika
Dieter Neher
Christian Koerner
Donato Spoltore
Koen Vandewal
eng
uncontrolled
energy losses
eng
uncontrolled
nonradiative recombination
eng
uncontrolled
open-circuit voltage
eng
uncontrolled
organic solar cells
eng
uncontrolled
voltage losses
Institut für Physik und Astronomie
Referiert
Import
37772
2014
2014
eng
12
4
review
SPIE
Bellingham
1
--
--
--
Toward bulk heterojunction polymer solar cells with thermally stable active layer morphology
When state-of-the-art bulk heterojunction organic solar cells with ideal morphology are exposed to prolonged storage or operation at elevated temperatures, a thermally induced disruption of the active layer blend can occur, in the form of a separation of donor and acceptor domains, leading to diminished photovoltaic performance. Toward the long-term use of organic solar cells in real-life conditions, an important challenge is, therefore, the development of devices with a thermally stable active layer morphology. Several routes are being explored, ranging from the use of high glass transition temperature, cross-linkable and/or side-chain functionalized donor and acceptor materials, to light-induced dimerization of the fullerene acceptor. A better fundamental understanding of the nature and underlying mechanisms of the phase separation and stabilization effects has been obtained through a variety of analytical, thermal analysis, and electro-optical techniques. Accelerated aging systems have been used to study the degradation kinetics of bulk heterojunction solar cells in situ at various temperatures to obtain aging models predicting solar cell lifetime. The following contribution gives an overview of the current insights regarding the intrinsic thermally induced aging effects and the proposed solutions, illustrated by examples of our own research groups. (C) The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License.
Journal of photonics for energy
10.1117/1.JPE.4.040997
1947-7988
wos:2014
040997
WOS:000338629200001
Cardinaletti, I (reprint author), Hasselt Univ, Inst Mat Res IMO IMOMEC, Wetenschapspk 1, B-3590 Diepenbeek, Belgium., ilaria.cardinaletti@uhasselt.be
Interreg-project ORGANEXT; Fund for Scientific Research, Flanders
(Belgium) (FWO)
Ilaria Cardinaletti
Jurgen Kesters
Sabine Bertho
Bert Conings
Fortunato Piersimoni
Laurence Lutsen
Milos Nesladek
Bruno Van Mele
Guy Van Assche
Koen Vandewal
Alberto Salleo
Dirk Vanderzande
Wouter Maes
Jean V. Manca
eng
uncontrolled
organic photovoltaics
eng
uncontrolled
bulk heterojunction
eng
uncontrolled
thermal stability
eng
uncontrolled
phase separation
eng
uncontrolled
lifetime
Institut für Physik und Astronomie
Referiert