Refine
Has Fulltext
- no (240)
Year of publication
Document Type
- Article (240) (remove)
Language
- English (240)
Is part of the Bibliography
- yes (240) (remove)
Keywords
- perovskite solar cells (10)
- organic solar cells (9)
- charge transport (4)
- conjugated polymers (4)
- morphology (4)
- Solar cells (3)
- non-fullerene acceptors (3)
- organic semiconductors (3)
- photovoltaic devices (3)
- polymer solar cells (3)
- solar cells (3)
- 2D perovskites (2)
- Organic electronics (2)
- Organic semiconductors (2)
- Organic solar cells (2)
- UV-vis spectroscopy (2)
- bulk heterojunction (2)
- carbon nitride (2)
- charge generation (2)
- charge transfer (2)
- conductivity (2)
- doping (2)
- driving force (2)
- hysteresis (2)
- mobility (2)
- nonfullerene acceptors (2)
- nonradiative recombination (2)
- open-circuit voltage (2)
- organic electronics (2)
- organic photovoltaics (2)
- perovskite solar cell (2)
- photocurrent generation (2)
- photoluminescence (2)
- quasi-Fermi level splitting (2)
- recombination (2)
- thin films (2)
- voltage losses (2)
- (Z)-isomer (1)
- Aggregate states (1)
- All-polymer heterojunctions (1)
- Alternating copolymers (1)
- Ambipolar charge transport (1)
- Ambipolar materials (1)
- Backbone modifications (1)
- Bilayer solar cells (1)
- Bulk heterojunction (1)
- CH center dot center dot center dot F hydrogen bonds (1)
- Capacitance spectroscopy (1)
- Carbon nitride (1)
- Carrier dynamics (1)
- Charge separation (1)
- Conformational disorder (1)
- Crystalline phases (1)
- Donor materials (1)
- Donor-acceptor copolymers (1)
- Doped semiconductors (1)
- Effect of sintering (1)
- Efficiency optimization (1)
- Electric polarization (1)
- Electrical properties and parameters (1)
- Electron traps (1)
- Electronic and spintronic devices (1)
- Electronics, photonics and device physics (1)
- Energetic disorder (1)
- Energy science and technology (1)
- Energy-level alignment (1)
- Fermi-level alignment (1)
- Fermi-level pinning (1)
- Hybrid solar cells (1)
- ISOS-L-1I protocol (1)
- Interface dipole (1)
- Interfaces (1)
- Interlayer (1)
- Intrachain order (1)
- Intragap states (1)
- Inverted solar cells (1)
- Kelvin probe (1)
- Linearly increasing voltage (CELIV) (1)
- Low band-gap (1)
- Low voltage losses (1)
- Microscopic morphology (1)
- Mobility imbalance (1)
- Mobility relaxation (1)
- Monte Carlo simulation (1)
- Multiple trapping model (1)
- Nonaqueous sol-gel (1)
- Nonradiative recombination (1)
- OFET (1)
- Open-circuit voltage (1)
- Optical modeling (1)
- Optoelectronic devices and components (1)
- Optoelectronic properties (1)
- Optoelectronics (1)
- Organic LEDs (1)
- PCPDTBT (1)
- PEDOT (1)
- Partially alternating copolymers (1)
- Perovskite solar cell (1)
- Photo-CELIV (1)
- Photocatalysis (1)
- Photoconductivity (1)
- Photocurrent (1)
- Photonic devices (1)
- Photovoltaic gap (1)
- Polymer infiltration (1)
- Polymer intermixing (1)
- Recombination losses (1)
- RhB degradation (1)
- RhB photodegradation (1)
- Semiconductors (1)
- SiO2 composite material (1)
- Solar energy and photovoltaic technology (1)
- Spectral diffusion (1)
- Statistical copolymers (1)
- Stille-type cross-coupling (1)
- Structure-property relationships (1)
- Sublimation with good yield (1)
- TCAD (1)
- Tandem solar cells (1)
- Thin nanocrystalline TiO2 layer (1)
- Time-dependent mobility (1)
- Time-of-flight (TOF) (1)
- Transient fluorescence (1)
- Transient photocurrent (1)
- Transport properties titania (1)
- UV nanoimprint lithography (1)
- Ultraviolet photoelectron spectroscopy (1)
- V-OC loss (1)
- Vacuum-level alignment (1)
- X-ray photoelectron spectroscopy (1)
- ZnO (1)
- absorption spectroscopy (1)
- aggregation (1)
- amorphous state (1)
- antireflection (1)
- aqueous solutions (1)
- built-in potential (1)
- cesium lead halides (1)
- characterization tools (1)
- charge accumulation (1)
- charge carrier extraction (1)
- charge carrier recombination (1)
- charge carrier transport (1)
- charge collection (1)
- charge generation layers (1)
- charge generation yield (1)
- charge injection across hybrid interfaces (1)
- charge recombination yield (1)
- charge selectivity (1)
- charge transfer states (1)
- charge transfers (1)
- charge transport layers (1)
- charge-transfer states (1)
- conducting polymer (1)
- conducting polymers (1)
- conformational analysis (1)
- conjugated polyelectrolytes (1)
- crystal orientation (1)
- crystalline ordering (1)
- crystallization (1)
- degradation (1)
- diffusion length (1)
- domain purity (1)
- donor-acceptor interfaces (1)
- double-layer (1)
- drift length (1)
- electro-optical materials (1)
- electrodes (1)
- electron contact (1)
- electron-transport layers (1)
- energetic disorders (1)
- energetic offset (1)
- energy gradients (1)
- energy losses (1)
- energy-level alignments (1)
- excess energy (1)
- excitonic materials (1)
- field-effect-transistor (1)
- figure of merit (1)
- fill factor (1)
- films (1)
- flexible (1)
- fluorescence (or Forster) (1)
- fluorinated organic spacer (1)
- fluorination (1)
- fullerene (1)
- fullerenes (1)
- geminate recombination (1)
- geometrical deformations (1)
- glycerol oxidation (1)
- heterojunction silicon solar cells (1)
- high performance polymers (1)
- hole extraction (1)
- hole selective materials (1)
- host-guest systems (1)
- hybrid metal oxides (1)
- inorganic perovskites (1)
- interaction parameter (1)
- interface engineering (1)
- interface recombination (1)
- interfaces (1)
- interfacial layers (1)
- lead halide perovskite films (1)
- lead halide perovskites (1)
- lifetime‐ mobility product (1)
- light management (1)
- light polarisation (1)
- light-emitting diodes (1)
- liquid crystal polymers (1)
- mesocrystals (1)
- metal oxide (1)
- metal-free photocatalysis (1)
- microscopy (1)
- mixed domains (1)
- mobile ions (1)
- molar mass distribution (1)
- molecular doping (1)
- molecular dynamics method (1)
- molecular weight (1)
- molecular weight distribution (1)
- molybdenum oxide (1)
- naphthalenediimide (1)
- non-Langevin recombination (1)
- non-Langevin reduction factors (1)
- non-radiative interface recombination (1)
- non-radiative recombination (1)
- nonradiative losses (1)
- nonradiative voltage losses (1)
- nucleation (1)
- optical hole burning (1)
- optical simulations (1)
- organic interfaces (1)
- organic light-emitting diode (1)
- organohalide lead perovskites (1)
- oxygen plasma (1)
- passivation (1)
- phase purity (1)
- phase transition (1)
- phase transitions (1)
- phosphonic acid (1)
- photochemistry (1)
- photophysics (1)
- photostability (1)
- poly(heptazine imide) (1)
- power conversion efficiency (1)
- quasi-Fermi level (1)
- quasi-steady-state photoinduced absorptions (1)
- random copolymer (1)
- recombinations (1)
- regular planar architecture (1)
- resonance energy transfer (1)
- resonant X-ray scattering (1)
- selective contact (1)
- self-assembled monolayers (1)
- semiconducting polymers (1)
- simulations (1)
- small molecules (1)
- spectroelectrochemistry (1)
- spin-related factors (1)
- spiro-OMeTAD (1)
- splitting (1)
- steady‐ state photoconductance (1)
- structure (1)
- sulfur (1)
- surface (1)
- surface band bending (1)
- surface modification (1)
- surface photovoltage (1)
- surface states (1)
- surface wetting (1)
- synthesis (1)
- tandem solar cells (1)
- temperature dependence (1)
- thermoresponsive polymers (1)
- thick junctions (1)
- thiophene (1)
- time of flight (1)
- transient absorption spectroscopy (1)
- transient spectroscopy (1)
- transport layer (1)
- transport layers (1)
- triple-cation perovskite (1)
- triplet excited states (1)
- ultraviolet photoelectron spectroscopy (1)
- upconversion (1)
- water reduction reactions (1)
- work function (1)
Institute
Light-induced softening of azobenzene dye-doped polymer films probed with quartz crystal resonators
(2000)
Improving the performance of doped p-conjugated polymers for use in organic light-emitting diodes
(2000)
Chiroptcial properties of poly(p-phenyleneethynylene) copolymers in thin films : large g-values
(2002)
Photoaddressable alignment layers for fluorescent polymers in polarized electroluminescence devices
(2002)
The delayed luminescence and phosphorescence of ladder-type methyl-poly(para-phenylene) (MeLPPP) doped with benzil at a concentration of 20% by weight has been measured. The introduction of benzil leads to a dramatic reduction of the polymer singlet emission. At the same time, a new band with maximum at 611 nm appears, corresponding to the phosphorescence of MeLPPP. The phosphorescence decay on the short time scale is close to an exponential law with a time decay of 15 ms. This indicates that benzil can efficiently sensitize the phosphorescence of the polymer. In addition, a broad and featureless emission is observed in the delayed luminescence spectra of benzil-doped MeLPPP, which is attributed to an exciplex formed between the polymer host and the dopant. We further observe that the delayed fluorescence is enhanced by the addition of benzil. It is concluded that the delayed fluorescence of benzil-doped MeLPPP is mainly due to the annihilation of triplet excitons on the polymer. Finally, efficient triplet-triplet energy transfer from the benzil-doped polymer to the red-emitting phosphorescent dye Pt(II)octaethylporphyrin is established. (C) 2004 American Institute of Physics
Alkoxy-substituted CN-containing phenylene-vinylene-alt-phenylene-ethynylene hybrid polymers (CN-PPV-PPE), 3a, 3b, and 7a, were obtained from luminophoric dialdehydes 1 by step growth polymerization via Knoevenagel reaction as high molecular-weight materials. Corresponding CN-free polymers 3c and 7b and an ethynylene-free polymer 5 with similar side chains were synthesized for the purpose of comparison. The chemical structures of the polymers were confirmed by IR, H-1 and C-13 NMR, and elemental analysis. Thermal characterization was conducted by means of thermogravimetric analysis and differential scanning calorimetry. Morphology was investigated by means of optical microscopy and small-angle light scattering. The final morphologies are determined by the molecular characteristics (side chains volume fraction, backbone stiffness) of the studied polymers. All the CN-containing polymers 3b, 5, and 7a exhibit higher fluorescence quantum yield in solid state (50 to 60%), but lower quantum yields (12-40%) in dilute chloroform solution, in total contrast to CN-free polymers 3c, 3d, and 7b. Identical optical, E-g(opt), and electrochemical band gap energies, E- g(ec), were obtained for 3b, 3c and 3d with intrinsic self-assembly ability, whereas a discrepancy, DeltaE(g), was observed in the cases of the fully substituted polymers 5, 7a, and 7b, whose values are dependent on the level of backbone stiffness and length of the side groups combined with the presence or absence of CN units. The incorporation of CN units in 3b and 7a lowers their respective LUMO level by 220 and 350 meV compared to their corresponding CN-free counterparts 3c and 7b, suggesting an improvement of the electron-accepting strength. Polymers 3b and 7a are efficient electron acceptors suitable for photovoltaic application. The experiments indicate that 3b is a better electron acceptor when used together with M3EH-PPV, but transport properties seem to be better for 7a. With 3b, high external quantum efficiencies of up to 23%, an open circuit voltage of up to 1.52 V, and a white light energy efficiency of 0.65% could be realized in bilayer solar cell devices. LED-devices of configuration ITO/PEDOT:PSS/polymer/Ca/Al from 3b, 3c, 7a, and 7b showed low turn-on voltages between 2 and 2.5 V. The CN-free polymers 3c and 7b exhibit far better EL parameters than their corresponding CN containing counterparts 3b and 7a
All parameters describing the charge carrier dynamics in a poly(phenylene vinylene)-based photorefractive (PR) composite relevant to PR grating dynamics were determined using photoconductivity studies under various illumination conditions. In particular, the values of the coefficients for trap filling and recombination of charges with ionized sensitizer molecules could be extracted independently. It is concluded that the PR growth time without preillumination is mostly determined by the competition between deep trap filling and recombination with ionized sensitizer molecules. Further, the pronounced increase in PR speed upon homogeneous preillumination (gating) as reported recently is quantitatively explained by deep trap filling
Aggregation of chromophores in the solid state commonly causes undesirable red shifts in the emission spectra and/or emission quenching. To overcome this problem, we have prepared soluble perylenetetracarboxidiimide dyes in which the chromophores are effectively shielded by polyphenylene dendrimers attached in the bay positions. Models show that attachment of the shielding units in the bay position should provide more efficient shielding than attaching them via the imide moieties. The dendrimers possess excellent film-forming properties due to alkyl substituents on their peripheries. The lack of a red shift in emission upon going from solution to the solid state indicates the dendrons suppress interaction of the emissive cores, leading to pure red-orange emission. Single-layer LEDs produce red-orange emission with relatively low efficiency especially for the higher generation dendrons, which is attributed to poor charge conduction. LEDs using blends of the dendrimers and the undendronized dye as a model compound in PVK have been investigated, and a model to extract relative charge injection rates through the dendritic scaffold from the spectral contributions in the EL spectra is developed
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
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
Energy transfer in a ladder-type methyl-poly(para-phenylene) doped by Pt(II)octaethylporphyrin
(2004)
The luminescence of a ladder-type methyl-poly(para-phenylene) (MeLPPP) doped by platinum-porphyrin dye PtOEP covering the concentration 10(-3) to 5% by weight has been measured employing cw and transient techniques. Upon excitating into the range of absorption of the host strong phosphorescence of the dopant is observed. Possible ways of populating of the dopant triplet state are considered. It is shown that the main channel is singlet-singlet energy transfer among chromophor groups of the polymer followed by Forster-type transfer to the guest and subsequent intersystem crossing. (C) 2003 Elsevier B.V. All rights reserved
The optical, structural, and electrical properties of thin layers made from poly(3-hexylthiophene) (P3HT) samples of different molecular weights are presented. As reported in a previous paper by Kline et al., Adv. Mater 2003, 15, 1519, the mobilities of these layers are a strong function of the molecular weight, with the largest mobility found for the largest molecular weight. Atomic force microscopy studies reveal a complex polycrystalline morphology which changes considerably upon annealing. X-ray studies show the occurrence of a layered phase for all P3HT fractions, especially after annealing at 1.50 degreesC . However, there is no clear correlation between the differences in the transport properties and the data from structural investigations. In order to reveal the processes limiting the mobility in these layers, the transistor properties were investigated as a function of temperature. The mobility decreases continuously with increasing temperatures; with the same trend pronounced thermochromic effects of the P3HT films occur. Apparently, the polymer chains adopt a more twisted, disordered conformation at higher temperatures, leading to interchain transport barriers. We conclude that the backbone conformation of the majority of the bulk material rather than the crystallinity of the layer is the most crucial parameter controlling the charge transport in these P3HT layers. This interpretation is supported by the significant blue-shift of the solid-state absorption spectra with decreasing molecular weight, which is indicative of a larger distortion of the P3HT backbone in the low-molecular weight P3HT layers
Suppression of the keto-emission in polyfluorene light-emitting diodes : Experiments and models
(2004)
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
Polymer solar cell devices with nanostructured blend layers have been fabricated using single- and dual- component polymer nanospheres. Starting from an electron-donating and an electron-accepting polyfluorene derivative, PFB and F8BT, dissolved in suitable organic solvents, dispersions of solid particles with mean diameters of ca. 50 nm, containing either the pure polymer components or a mixture of PFB and F8BT in each particle, were prepared with the miniemulsion process. Photovoltaic devices based on these particles have been studied with respect to the correlation between external quantum efficiency and layer composition. It is shown that the properties of devices containing a blend of single-component PFB and F8BT particles differ significantly from those of solar cells based on blend particles, even for the same layer composition. Various factors determining the quantum efficiency in both kinds of devices are identified and discussed, taking into account the spectroscopic properties of the particles. An external quantum efficiency of ca. 4% is measured for a device made from polymer blend nanoparticles containing PFB:F8BT at a weight ratio of 1:2 in each individual nanosphere. This is among the highest values reported so far for photovoltaic cells using this material combination
Materials for polymer electronics applications semiconducting polymer thin films and nanoparticles
(2004)
The paper presents two different approaches to nanostructured semiconducting polymer materials: (i) the generation of aqueous semiconducting polymer dispersions (semiconducting polymer nanospheres SPNs) and their processing into dense films and layers, and (ii) the synthesis of novel semiconducting polyfluorene-block-polyaniline (PF-b-PANI) block copolymers composed of conjugated blocks of different redox potentials which form nanosized morphologies in the solid state
Optically induced mass transport studied by scanning near-field optical- and atomic force microscopy
(2004)
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
The luminescence of a ladder-type methyl-poly(para-phenylene) (MeLPPP) doped with platinum-porphyrin dye PtOEP covering the concentration 10(-3)-5% by weight has been measured employing cw and transient techniques. Upon excitation into the range of absorption of the host, strong phosphorescence of the dopant is observed. Possible ways of populating the dopant triplet state are considered. (c) 2004 Elsevier B.V. All rights reserved
It is well known that the performance of solar cells based on a blend of hole-accepting and electron-accepting conjugated polymers as the active material depend crucially on the length scale of the resulting phase separated morphology. However, a direct control of this morphology is difficult if the layer is prepared from an organic solvent. To circumvent this difficulty, recently a universal method to fabricate defined nano-structured blend layer using nanoparticles dispersed in water was demonstrated. These nanoparticles were prepared with the miniemulsion method, which allows for the preparation of semiconducting polymer nanospheres (SPNs) with diameters in the range of 30 to 300 nanometres. Since the process starts from the active material dissolved in a common solvent, it can be applied to the fabrication of nanoparticles of blends of polymers with oligomers or even with inorganic materials. We present here for the first time scanning near field optical microscopy (SNOM) investigations on these novel nanostructured polymer layers. We show that by spin-coating a mixture of two different dispersions a nanoparticle monolayer with a statistically distribution of the nanoparticles can be obtained. Mixing conjugated polymer nanoparticles with some inert particles like polystyrene beads may allow for the preparation of nano-sized light emitters
An increase in random molecular vibrations of a solid owing to heating above the melting point leads to a decrease in its long-range order and a loss of structural symmetry. Therefore conventional liquids are isotropic media. Here we report on a light-induced isothermal transition of a polymer film from an isotropic solid to an anisotropic liquid state in which the degree of mechanical anisotropy can be controlled by light. Whereas during irradiation by circular polarized light the film behaves as an isotropic viscoelastic fluid, it shows considerable fluidity only in the direction parallel to the light field vector under linear polarized light. The fluidization phenomenon is related to photoinduced motion of azobenzene-functionalized molecular units, which can be effectively activated only when their transition dipole moments are oriented close to the direction of the light polarization. We also describe here how the photofluidization allows nanoscopic elements of matter to be precisely manipulated