Refine
Has Fulltext
- no (233)
Year of publication
Document Type
- Article (233) (remove)
Language
- English (233)
Is part of the Bibliography
- yes (233)
Keywords
- organic solar cells (11)
- perovskite solar cells (10)
- morphology (5)
- solar cells (5)
- charge transport (4)
- conjugated polymers (4)
- non-fullerene acceptors (4)
- voltage losses (4)
- Solar cells (3)
- open-circuit voltage (3)
- organic photovoltaics (3)
- organic semiconductors (3)
- photoluminescence (3)
- photovoltaic devices (3)
- polymer solar cells (3)
- 2D perovskites (2)
- Organic electronics (2)
- Organic semiconductors (2)
- Organic solar cells (2)
- UV-vis spectroscopy (2)
- carbon nitride (2)
- charge generation (2)
- charge transfer (2)
- charge-transfer states (2)
- conductivity (2)
- doping (2)
- driving force (2)
- hysteresis (2)
- inorganic perovskites (2)
- interface recombination (2)
- nonfullerene acceptors (2)
- nonradiative recombination (2)
- organic electronics (2)
- perovskite solar cell (2)
- photocurrent generation (2)
- quasi-Fermi level splitting (2)
- recombination (2)
- thin films (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)
- C60 (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)
- CsPbI2Br (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)
- Frank-Condon analysis (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)
- built-in potential (1)
- bulk heterojunction (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 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)
- conducting polymer (1)
- conducting polymers (1)
- conformational analysis (1)
- crystal orientation (1)
- crystalline ordering (1)
- crystallization (1)
- defects (1)
- degradation (1)
- diffusion length (1)
- domain purity (1)
- donor-acceptor interfaces (1)
- double-layer (1)
- drift length (1)
- efficiency potentials (1)
- electro-optical materials (1)
- electrodes (1)
- electron contact (1)
- electron-transport layers (1)
- energetic disorder (1)
- energetic disorders (1)
- energetic offset (1)
- energy gradients (1)
- energy losses (1)
- energy-level alignments (1)
- excess energy (1)
- excitonic materials (1)
- external quantum efficiency (1)
- field-effect-transistor (1)
- figure of merit (1)
- fill factor (1)
- films (1)
- flexible (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)
- interaction parameter (1)
- interface engineering (1)
- interfaces (1)
- interfacial layers (1)
- lead halide perovskite films (1)
- lifetime‐ mobility product (1)
- light management (1)
- light polarisation (1)
- light-emitting diodes (1)
- liquid crystal polymers (1)
- loss mechanisms (1)
- mesocrystals (1)
- metal oxide (1)
- metal-free photocatalysis (1)
- microscopy (1)
- mixed domains (1)
- mobile ions (1)
- mobility (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)
- perovskites (1)
- phase purity (1)
- phase transition (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)
- 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)
- ternary blends (1)
- thick junctions (1)
- thiophene (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
- Institut für Physik und Astronomie (233) (remove)
Cost-efficient, visible-light-driven hydrogen production from water is an attractive potential source of clean, sustainable fuel. Here, it is shown that thermal solid state reactions of traditional carbon nitride precursors (cyanamide, melamine) with NaCl, KCl, or CsCl are a cheap and straightforward way to prepare poly(heptazine imide) alkali metal salts, whose thermodynamic stability decreases upon the increase of the metal atom size. The chemical structure of the prepared salts is confirmed by the results of X-ray photoelectron and infrared spectroscopies, powder X-ray diffraction and electron microscopy studies, and, in the case of sodium poly(heptazine imide), additionally by atomic pair distribution function analysis and 2D powder X-ray diffraction pattern simulations. In contrast, reactions with LiCl yield thermodynamically stable poly(triazine imides). Owing to the metastability and high structural order, the obtained heptazine imide salts are found to be highly active photo-catalysts in Rhodamine B and 4-chlorophenol degradation, and Pt-assisted sacrificial water reduction reactions under visible light irradiation. The measured hydrogen evolution rates are up to four times higher than those provided by a benchmark photocatalyst, mesoporous graphitic carbon nitride. Moreover, the products are able to photocatalytically reduce water with considerable reaction rates, even when glycerol is used as a sacrificial hole scavenger.
A water soluble fluorescent polymer as a dual colour sensor for temperature and a specific protein
(2013)
We present two thermoresponsive water soluble copolymers prepared via free radical statistical copolymerization of N-isopropylacrylamide (NIPAm) and of oligo(ethylene glycol) methacrylates (OEGMAs), respectively, with a solvatochromic 7-(diethylamino)-3-carboxy-coumarin (DEAC)-functionalized monomer. In aqueous solutions, the NIPAm-based copolymer exhibits characteristic changes in its fluorescence profile in response to a change in solution temperature as well as to the presence of a specific protein, namely an anti-DEAC antibody. This polymer emits only weakly at low temperatures, but exhibits a marked fluorescence enhancement accompanied by a change in its emission colour when heated above its cloud point. Such drastic changes in the fluorescence and absorbance spectra are observed also upon injection of the anti-DEAC antibody, attributed to the specific binding of the antibody to DEAC moieties. Importantly, protein binding occurs exclusively when the polymer is in the well hydrated state below the cloud point, enabling a temperature control on the molecular recognition event. On the other hand, heating of the polymer-antibody complexes releases a fraction of the bound antibody. In the presence of the DEAC-functionalized monomer in this mixture, the released antibody competitively binds to the monomer and the antibody-free chains of the polymer undergo a more effective collapse and inter-aggregation. In contrast, the emission properties of the OEGMA-based analogous copolymer are rather insensitive to the thermally induced phase transition or to antibody binding. These opposite behaviours underline the need for a carefully tailored molecular design of responsive polymers aimed at specific applications, such as biosensing.
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.
In this work, the authors present a 7.5% efficient hybrid tandem solar cell with the bottom cell made of amorphous silicon and a Si-PCPDTBT:PC70BM bulk heterojunction top cell. Loss-free recombination contacts were realized by combing Al-doped ZnO with either the conducting polymer composite PEDOT:PSS or with a bilayer of ultrathin Al and MoO3. Optimization of these contacts results in tandem cells with high fill factors of 70% and an open circuit voltage close to the sum of those of the sub-cells. This is the best efficiency reported for this type of hybrid tandem cell so far. Optical and electrical device modeling suggests that the efficiency can be increased to similar to 12% on combining a donor polymer with suitable absorption onset with PCBM. We also describe proof-of-principle studies employing light trapping in hybrid tandem solar cells, suggesting that this device architecture has the potential to achieve efficiencies well above 12%. (C) 2014 Elsevier B.V. All rights reserved.
The effect of oxygen plasma treatment and/or silanization with hexamethyldisilazane (HMDS) on the surface chemistry and the morphology of the SiO2-gate insulator were studied with respect to the performance of organic field effect transistors. Using X-ray photoelectron spectroscopy (XPS), it is shown that silanization leads to the growth of a polysiloxane interfacial layer and that longer silanization times increase the thickness of this layer. Most important, silanization reduces the signal from surface contaminations such as oxidized hydrocarbon molecules. In fact, the lowest concentration of these contaminations was found after a combined oxygen plasma/silanization treatment. The results of these investigations were correlated with the characteristic device parameters of polymer field effect transistors with poly(3-hexylthiophene)s as the semiconducting layer. We found that the field effect mobility correlates with the concentration of contaminations as measured by XPS. We, finally, demonstrate that silanization significantly improves the operational stability of the device in air compared to the untreated devices
An original set of experimental and modeling tools is used to quantify the yield of each of the physical processes leading to photocurrent generation in organic bulk heterojunction solar cells, enabling evaluation of materials and processing condition beyond the trivial comparison of device performances. Transient absorption spectroscopy, “the” technique to monitor all intermediate states over the entire relevant timescale, is combined with time-delayed collection field experiments, transfer matrix simulations, spectral deconvolution, and parametrization of the charge carrier recombination by a two-pool model, allowing quantification of densities of excitons and charges and extrapolation of their kinetics to device-relevant conditions. Photon absorption, charge transfer, charge separation, and charge extraction are all quantified for two recently developed wide-bandgap donor polymers: poly(4,8-bis((2-ethylhexyl)oxy)benzo[1,2-b:4,5-b′]dithiophene-3,4-difluorothiophene) (PBDT[2F]T) and its nonfluorinated counterpart poly(4,8-bis((2-ethylhexyl)oxy)benzo[1,2-b:4,5-b′]dithiophene-3,4-thiophene) (PBDT[2H]T) combined with PC71BM in bulk heterojunctions. The product of these yields is shown to agree well with the devices' external quantum efficiency. This methodology elucidates in the specific case studied here the origin of improved photocurrents obtained when using PBDT[2F]T instead of PBDT[2H]T as well as upon using solvent additives. Furthermore, a higher charge transfer (CT)-state energy is shown to lead to significantly lower energy losses (resulting in higher VOC) during charge generation compared to P3HT:PCBM.
We investigate charge transport in a high-electron mobility polymer, poly(N, N-bis 2-octyldodecyl-naphthalene-1,4,5,8-bis dicarboximide-2,6-diyl-alt-5,5-2,2-bithiophene) [P(NDI2OD-T2), Polyera ActivInk (TM) N2200]. Time-of-flight measurements reveal electron mobilities approaching those measured in field-effect transistors, the highest ever recorded in a conjugated polymer using this technique. The modest temperature dependence and weak dispersion of the transients indicate low energetic disorder in this material. Steady-state electron-only current measurements reveal a barrier to injection of about 300 meV. We propose that this barrier is located within the P(NDI2OD-T2) film and arises from molecular orientation effects.
The electrical conductivity of organic semiconductors can be enhanced by orders of magnitude via doping with strong molecular electron acceptors or donors. Ground-state integer charge transfer and charge-transfer complex formation between organic semiconductors and molecular dopants have been suggested as the microscopic mechanisms causing these profound changes in electrical materials properties. Here, we study charge-transfer interactions between the common molecular p-dopant 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane and a systematic series of thiophene-based copolymers by a combination of spectroscopic techniques and electrical measurements. Subtle variations in chemical structure are seen to significantly impact the nature of the charge-transfer species and the efficiency of the doping process, underlining the need for a more detailed understanding of the microscopic doping mechanism in organic semiconductors to reliably guide targeted chemical design.