A5082397926- Semiconductor Quantum Structures and Devices
- Thin-Film Transistor Technologies
- Nanowire Synthesis and Applications
- Chalcogenide Semiconductor Thin Films
- solar cell performance optimization
- Perovskite Materials and Applications
- Quantum Dots Synthesis And Properties
- Silicon and Solar Cell Technologies
- Silicon Nanostructures and Photoluminescence
- Quantum and electron transport phenomena
- Semiconductor materials and interfaces
- Advancements in Semiconductor Devices and Circuit Design
- Advanced Thermodynamics and Statistical Mechanics
- Surface and Thin Film Phenomena
- Organic Light-Emitting Diodes Research
- Conducting polymers and applications
- Organic Electronics and Photovoltaics
- Molecular Junctions and Nanostructures
- Gyrotron and Vacuum Electronics Research
- Semiconductor Lasers and Optical Devices
- Electron and X-Ray Spectroscopy Techniques
- Thermal Radiation and Cooling Technologies
- Advanced Semiconductor Detectors and Materials
- Photonic Crystals and Applications
- Quantum, superfluid, helium dynamics
ETH Zurich
2020-2025
Fluxim (Switzerland)
2019-2024
Sulzer (Switzerland)
2019-2024
Board of the Swiss Federal Institutes of Technology
2023-2024
École Polytechnique Fédérale de Lausanne
2022
ZHAW Zurich University of Applied Sciences
2022
Forschungszentrum Jülich
2012-2021
Stadtwerke Jülich (Germany)
2017-2018
Paul Scherrer Institute
2005-2008
University of Bern
1983
We present a microscopic theory of bipolar quantum well structures in the photovoltaic regime, based on non-equilibrium Green's function formalism for multi band tight binding Hamiltonian. The kinetic equations single particle functions electrons and holes are self-consistently coupled to Poisson's equation, including inter-carrier scattering Hartree level. Relaxation broadening mechanisms considered by inclusion acoustic optical electron-phonon interaction self consistent Born approximation...
We report on the systematic optimization of intrinsic amorphous silicon oxide buffer layer in interplay with doped microcrystalline contact layers for heterojunction solar cells using all based functional flat p-type float-zone wafers. While surface passivation quality is comparably good within a wide range low oxygen contents, optical band gap increases and dark conductivity decreases increasing content, giving rise to an inevitable trade-off between transparency electrical conductivity. On...
In optoelectronic devices such as solar cells and photodetectors, a portion of electron-hole pairs are generated so called hot carriers with an excess energy that is typically lost heat. The long standing aim to harvest this enhance device performance has proven be very challenging, largely due the extremely short-lived nature carriers. Efforts thus focus on increasing carrier relaxation time, tailoring heterostructures allow for hot-carrier extraction short time- length-scales. Recently,...
Abstract This Letter reports on the fabrication and characterization of silicon heterojunction solar cells with oxide based buffer (intrinsic amorphous oxide) contact layers (doped microcrystalline flat p‐type wafers. The critical dependency cell performance front rear layer thickness reveals a trade‐off between open circuit voltage V oc fill factor FF. At optimum, highest efficiency 18.5% (active area = 0.67 cm 2 ) was achieved 664 mV, short current J sc 35.7 mA/cm FF 78.0%. (© 2012...
This paper reports on the development of phosphorous doped microcrystalline silicon oxide (µc-SiO x :H) films as an emitter window layer in flat p-type heterojunction (SHJ) solar cells featuring intrinsic a-SiO :H buffer layers. We investigated material properties n-type µc-SiO grown at various input gas ratios and correlated results SHJ utilizing varying oxygen content thickness to corresponding film properties. A maximum efficiency 19.0% was achieved. The excellent short circuit current...
For applications in luminescent solar concentrators harvesting subgap photons, either via direct irradiation of cells with optimized band gap or sensitization an up-conversion process, exact knowledge and tunability both the spectral shape intensity emission are paramount importance. In this work, we investigate theoretically photoluminescence spectra colloidal core-shell PbSe/PbS QDs type II alignments valence band. The method builds on a steady-state formulation non-equilibrium Greens...
The photovoltaic reciprocity theory relates the electroluminescence spectrum of a solar cell under applied bias to external quantum efficiency device as measured at short circuit conditions. Its derivation is based on detailed balance relations between local absorption and emission rates in optically isotropic media with non-degenerate quasi-equilibrium carrier distributions. In many cases, dependence density spatial variation electronic optical states point operation modest relation holds....
Photovoltaics—a mature technology—is set to play a vital role in achieving carbon-free energy system. This article examines the pivotal of optics advancing photovoltaics. We identify key scientific research areas where community can make significant contributions. are guided by central question: How facilitate large-scale deployment photovoltaics necessary for decarbonizing our societies?
The influence of Rashba spin-orbit coupling on zero conductance resonances appearing in one-dimensional conducting rings asymmetrically coupled to two leads is investigated. For this purpose, the transmission function corresponding one-electron scattering problem derived analytically and analyzed complex energy plane with focus zero-pole structure characteristic (anti)resonances. lifting real zeros due asymmetric Aharonov-Casher ring related breaking spin reversal symmetry analogy...
A quantum kinetic theory of direct and phonon-mediated indirect optical transitions is developed within the framework nonequilibrium Green's function formalism. After validation against standard Fermi golden rule approach in bulk case, it used simulation photocurrent generation ultrathin crystalline silicon $p$-$i$-$n$ junction devices.
Si-SiOx superlattices are among the candidates that have been proposed as high band gap absorber material in all-Si tandem solar cell devices. Owing to large potential barriers for photoexited charge carriers, transport these devices is restricted quantum-confined superlattice states. As a consequence of finite number wells and built-in fields, electronic spectrum can deviate considerably from minibands regular superlattice. In this article, quantum-kinetic theory based on non-equilibrium...
This paper reports on the analysis and optimization of high-efficiency organic tandem solar cells via full opto-electronic device simulation continuum level using a hopping model for explicit description charge recombination junction. Inclusion electrical sub-cell interconnection allows rigorous assessment impact internal distribution associated built-in fields as well quasi-Fermi profiles measured characteristics. It enables direct evaluation external quantum efficiency in that follows...
Photovoltaics—a mature technology—is set to play a vital role in achieving carbon-free energy system. This article examines the pivotal of optics advancing photovoltaics. We identify key scientific research areas where community can make significant contributions. are guided by central question: How facilitate large-scale deployment photovoltaics necessary for decarbonizing our societies?
Photovoltaics—a mature technology—is set to play a vital role in achieving carbon-free energy system. This article examines the pivotal of optics advancing photovoltaics. We identify key scientific research areas where community can make significant contributions. are guided by central question: How facilitate large-scale deployment photovoltaics necessary for decarbonizing our societies?
The generation of photocurrents due to coupling electrons both classical and quantized electromagnetic fields in thin semiconductor films is described within the framework nonequilibrium Green's function formalism. For coherent corresponding single field operator averages, an effective two-time intraband self-energy derived from a band decoupling procedure. evaluation photogeneration performed self-consistently with propagation by using for latter transfer matrix formalism extinction...
Abstract Malonylmethyl radical I [· CH 2 CH(COOEt) ] and its thioester analogue II (COSEt)] were generated by standard photolytic thermolytic methods from perester bromo precursors. The structures of examined ESR spectroscopy found to exist in preferred conformations. However, no indication for their rearrangement 1,2‐shift either an ethoxycarboxyl or (ethylthio)carbonyl group the corresponding succinyl radicals III IV , respectively, was at temperatures below − 40°C. At higher up 140°C,...
Many advanced concepts for high-efficiency photovoltaic devices exploit the peculiar optoelectronic properties of semiconductor nanostructures such as quantum wells, wires and dots. While optics is only modestly affected due to small size structures, optical transitions electronic transport can strongly deviate from simple bulk picture known conventional solar cell devices. This review article discusses challenges an adequate theoretical description device operation arising introduction...
This Topical Review discusses insights into the physical mechanisms of nanostructure solar cell operation as provided by numerical device simulation using a state-of-the-art quantum-kinetic framework based on non-equilibrium Green's function formalism. After brief introduction to field photovoltaics and an overview existing literature theoretical description experimental implementation such devices, formulation photovoltaic processes is discussed in detail, together with more conventional...
The photovoltaic characteristics of an ultra-thin GaAs solar cell with gold back reflector are simulated using the standard semi-classical drift-diffusion-Poisson model and advanced microscopic quantum-kinetic approach based on nonequilibrium Green's function (NEGF) formalism. For assumption flat band bulk absorption coefficient used in model, substantial qualitative quantitative discrepancies identified between results two approaches. agreement is improved by consideration field dependent...
An optical dyadic Green's function framework to describe the transverse electromagnetic fields in a planar perovskite solar-cell stack is coupled an electronic drift-diffusion model for rigorous treatment of photon recycling wave-optics regime realistic photovoltaic device. The provides local reabsorption rate as well detailed-balance compatible radiative prefactor, which are used achieve self-consistent solution that yields full optoelectronic device characteristics. presented approach...