A5051915613- Organic Electronics and Photovoltaics
- Conducting polymers and applications
- Perovskite Materials and Applications
- Thin-Film Transistor Technologies
- Organic Light-Emitting Diodes Research
- Nanowire Synthesis and Applications
- Particle accelerators and beam dynamics
- Electron and X-Ray Spectroscopy Techniques
- Molecular Junctions and Nanostructures
- Silicon and Solar Cell Technologies
- Advanced X-ray Imaging Techniques
- Laser Design and Applications
- Particle Accelerators and Free-Electron Lasers
- X-ray Spectroscopy and Fluorescence Analysis
- Fullerene Chemistry and Applications
- solar cell performance optimization
- Radiation Therapy and Dosimetry
- Nuclear Physics and Applications
- Laser-Plasma Interactions and Diagnostics
- Laser-Matter Interactions and Applications
- Pulsed Power Technology Applications
- Semiconductor Lasers and Optical Devices
- Crystallography and Radiation Phenomena
- Superconducting Materials and Applications
- Laser-induced spectroscopy and plasma
University of Potsdam
2012-2022
CEA Paris-Saclay
1972-1973
Commissariat à l'Énergie Atomique et aux Énergies Alternatives
1972
Among the parameters that characterize a solar cell and define its power-conversion efficiency, fill factor is least well understood, making targeted improvements difficult. Here we quantify competition between charge extraction recombination by using single parameter θ, demonstrate this directly related to of many different bulk-heterojunction cells. Our finding supported experimental measurements on 15 donor:acceptor combinations, as drift-diffusion simulations organic cells in which...
Abstract The authors present efficient all‐polymer solar cells comprising two different low‐bandgap naphthalenediimide (NDI)‐based copolymers as acceptors and regioregular P3HT the donor. It is shown that these naphthalene have a strong tendency to preaggregate in specific organic solvents, preaggregation can be completely suppressed when using suitable solvents with large highly polarizable aromatic cores. Organic prepared from such nonaggregated polymer solutions show dramatically...
Developing novel materials and device architectures to further enhance the efficiency of polymer solar cells requires a fundamental understanding impact chemical structures on photovoltaic properties. Given that characteristics depend many parameters, deriving structure–property relationships has been very challenging. Here we report single parameter, hole mobility, determines fill factor several hundred nanometer thick bulk heterojunction devices based series copolymers with varying amount...
A long standing question in organic electronics concerns the effects of molecular orientation at donor/acceptor heterojunctions. Given a well-controlled bilayer system, we uncover genuine on charge generation and recombination. These are studied through point view photovoltaics-however, results have important implications operation all optoelectronic devices with interfaces, such as light emitting diodes photodetectors. Our findings can be summarized by two points. First, donor molecules...
The optical transition radiation emitted by electron-irradiated aluminum, silver, gold-coated plates, and self-supported aluminum Mylar films has been investigated experimentally. investigation was made with an electron beam incident at 45 °, having a mean intensity of 1 μA, energy which varied from 35 up to 72 MeV (68.5<γ<140.9). study the angular distribution degree polarization shown that high-directivity is around direction specular reflection contribution bremsstrahlung...
New polymers with high electron mobilities have spurred research in organic solar cells using polymeric rather than fullerene acceptors due to their potential of increased diversity, stability, and scalability. However, all‐polymer struggled keep up the steadily increasing power conversion efficiency polymer:fullerene cells. The lack knowledge about dominant recombination process as well missing concluding picture on role semi‐crystalline microstructure conjugated free charge carrier...
Abstract The functionality of organic semiconductor devices crucially depends on molecular energies, namely the ionisation energy and electron affinity. Ionisation affinity values thin films are, however, sensitive to film morphology composition, making their prediction challenging. In a combined experimental simulation study zinc-phthalocyanine its fluorinated derivatives, we show that changes in as function orientation neat or mixing ratio blends are proportional quadrupole component along...
The fact that organic solar cells perform efficiently despite the low dielectric constant of most photoactive blends initiated a long-standing debate regarding dominant pathways free charge formation. Here, we address this issue through accurate measurement activation energy for photogeneration over wide range photon energy, using method time-delayed collection field. For our prototypical bandgap polymer:fullerene blends, find neither temperature nor field dependence generation depend on...
Abstract A critical bottleneck for improving the performance of organic solar cells (OSC) is minimising non-radiative losses in interfacial charge-transfer (CT) state via formation hybrid energetic states. This requires small offsets often detrimental high external quantum efficiency (EQE). Here, we obtain OSC with both voltage (0.24 V) and photocurrent (EQE > 80%) simultaneously minimised. The CT states separate into free carriers ≈40-ps time constant. We combine device spectroscopic...
Abstract Fullerene‐based acceptors have dominated organic solar cells for almost two decades. It is only within the last few years that alternative rival their dominance, introducing much more flexibility in optoelectronic properties of these material blends. However, a fundamental physical understanding processes drive charge separation at heterojunctions still missing, but urgently needed to direct further improvements. Here combined experimental and theoretical approach used understand...
Photogeneration, recombination, and transport of free charge carriers in all-polymer bulk heterojunction solar cells incorporating poly(3-hexylthiophene) (P3HT) as donor poly([N,N'-bis(2-octyldodecyl)-naphthelene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5'-(2,2'-bithiophene)) (P(NDI2OD-T2)) acceptor polymer have been investigated by the use time delayed collection field (TDCF) time-of-flight (TOF) measurements. Depending on preparation procedure used to dry active layers, these comprise...
Hybrid multijunction solar cells comprising hydrogenated amorphous silicon and an organic bulk heterojunction are presented, reaching 11.7% power conversion efficiency. The benefits of merging inorganic subcells pointed out, the optimization cells, including optical modeling predictions tuning recombination contact described, outlook this technique is given.
Abstract The interplay between free charge carriers, transfer (CT) states and singlet excitons (S 1 ) determines the recombination pathway resulting open circuit voltage ( V OC of organic solar cells. By combining a well‐aggregated low bandgap polymer with different blend ratios fullerenes PCBM ICBA, energy CT state E is varied by 130 meV while leaving S () unaffected. It found that exciton dominates radiative properties when approaches , remains limited non‐radiative decay state. concluded...
The charge generation and recombination processes following photoexcitation of a low-bandgap polymer:perylene diimide photovoltaic blend are investigated by transient absorption pump–probe spectroscopy covering dynamic range from femto- to microseconds get insight into the efficiency-limiting photophysical processes. photoinduced electron transfer polymer perylene acceptor takes up several tens picoseconds, its efficiency is only half that in polymer:fullerene blend. This reduces...
Fluorinating conjugated polymers is a proven strategy for creating high performance materials in polymer solar cells, yet few studies have investigated the importance of fluorination method. We compare three fluorinated systems: poly(benzodithieno-dithienyltriazole) (PBnDT-XTAZ) random copolymer where 50% acceptor units are difluorinated, PBnDT-mFTAZ every unit monofluorinated, and 1:1 physical blend difluorinated nonfluorinated polymer. All systems same degree (50%) via different methods...
Power conversion efficiencies of donor/acceptor organic solar cells utilizing nonfullerene acceptors have now increased beyond the record their fullerene-based counterparts. There remain many fundamental questions regarding nanomorphology, interfacial states, charge generation and extraction, losses in these systems. Herein, we present a comparative study bulk heterojunction composed recently introduced naphthothiadiazole-based polymer (NT812) as electron donor two different acceptor...
Optical transition radiation produced by 40-60 MeV electrons crossing thin metallic foils has been studied in order to provide a beam diagnostic device. The yield is roughly one photon per 100 and the intensity appears be Z independent ; influence of bremsstrahlung then fairly weak. Measurements angular γ dependence, spectral density polarisation have carried out results are good agreement with theories. When multiple scattering angles negligible (< γ-1), strong eneray close γ3 , light...
We employed bias-assisted charge extraction techniques to investigate the transient and steady-state recombination of photogenerated carriers in complete devices a disordered polymer-fullerene blend. Charge is shown be dispersive, with significant slowdown rate over time, consistent results from kinetic Monte Carlo simulations. Surprisingly, our experiments reveal little no contributions early time nonequilibrated properties. conclude that energetic relaxation outpaces any nongeminate under...
Abstract Organic photovoltaics (PV) is an energy-harvesting technology that offers many advantages, such as flexibility, low weight and cost, well environmentally benign materials 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 high losses open-circuit voltage. Understanding improving open circuit voltage solar cells challenging, it controlled by properties a...
Alternative electron acceptors are being actively explored in order to advance the development of bulk-heterojunction (BHJ) organic solar cells (OSCs). The indene–C60 bisadduct (ICBA) has been regarded as a promising candidate, it provides high open-circuit voltage BHJ cells; however, photovoltaic performance such ICBA-based devices is often inferior when compared with omnipresent PCBM acceptor. Here, by pairing polymer (FTAZ) donor either or ICBA acceptor, we explore physical mechanism...
Th optical transitionradiatio emitted by electron irradiated aluminum, silver, gold-coated plates and self-supported metallic mylar films has been investigated experimental ly using 450 incident beams with intensities°from 100 pA up to 10 , A, energies from 35 72 MeV. Beam dignostics (intensity, profile, centering, energy) were made an ppropriae rrangment together a two-parallel foilsdevice in which the interference phenomena transiti. on radiation at both interfaces was exploited. The...