A5011004401- Chalcogenide Semiconductor Thin Films
- Quantum Dots Synthesis And Properties
- Copper-based nanomaterials and applications
- Perovskite Materials and Applications
- Semiconductor materials and interfaces
- Silicon and Solar Cell Technologies
- Thin-Film Transistor Technologies
- Conducting polymers and applications
- Silicon Nanostructures and Photoluminescence
- Advanced Semiconductor Detectors and Materials
- Semiconductor Quantum Structures and Devices
- Electronic and Structural Properties of Oxides
- solar cell performance optimization
- Phase-change materials and chalcogenides
- ZnO doping and properties
- Advanced Thermoelectric Materials and Devices
- Crystal Structures and Properties
- Solid-state spectroscopy and crystallography
- Organic Electronics and Photovoltaics
- nanoparticles nucleation surface interactions
- Machine Learning in Materials Science
- 2D Materials and Applications
- Surface and Thin Film Phenomena
- Magnetic and transport properties of perovskites and related materials
- Semiconductor Lasers and Optical Devices
Helmholtz-Zentrum Berlin für Materialien und Energie
2016-2025
University of Cambridge
2024
Duke University
2021
Shinshu University
2014
University of Limerick
2013
German Orient Foundation
2005-2009
Fraunhofer Institute for Telecommunications, Heinrich Hertz Institute
2004-2008
National Renewable Energy Laboratory
1995-2008
Max-Born-Institute for Nonlinear Optics and Short Pulse Spectroscopy
2003-2005
Carl von Ossietzky Universität Oldenburg
1999-2004
Tandem solar cells that pair silicon with a metal halide perovskite are promising option for surpassing the single-cell efficiency limit. We report monolithic perovskite/silicon tandem certified power conversion of 29.15%. The absorber, bandgap 1.68 electron volts, remained phase-stable under illumination through combination fast hole extraction and minimized nonradiative recombination at hole-selective interface. These features were made possible by self-assembled, methyl-substituted...
We introduce new hole-selective contacts for next-generation perovskite photovoltaics and point to design paths molecular engineering of perfect interfaces.
Charge transport layers (CTLs) are key components of diffusion controlled perovskite solar cells, however, they can induce additional non-radiative recombination pathways which limit the open circuit voltage (V_OC) cell. In order to realize full thermodynamic potential absorber, both electron and hole layer (ETL/HTL) need be as selective possible. By measuring quasi-Fermi level splitting (QFLS) perovskite/CTL heterojunctions, we quantify interfacial current for a wide range commonly used...
Abstract Photoluminescence spectroscopy is a widely applied characterization technique for semiconductor materials in general and halide perovskite solar cell particular. It can give direct information on the recombination kinetics processes as well internal electrochemical potential of free charge carriers single layers, layer stacks with transport complete cells. The correct evaluation interpretation photoluminescence requires consideration proper excitation conditions, calibration...
Abstract Today's perovskite solar cells (PSCs) are limited mainly by their open‐circuit voltage ( V OC ) due to nonradiative recombination. Therefore, a comprehensive understanding of the relevant recombination pathways is needed. Here, intensity‐dependent measurements quasi‐Fermi level splitting (QFLS) and on very same devices, including pin‐type PSCs with efficiencies above 20%, performed. It found that QFLS in lies significantly below its radiative limit for all intensities but also...
We demonstrate open-circuit voltages exceeding 1.26 V for inverted planar CH3NH3PbI3 solar cells fabricated using a combination of lead acetate and PbCl2 precursors leading to smooth films large grain sizes. Surface recombination is suppressed by careful optimization the PTAA hole transport PCBM electron layers. Suppression bulk surface verified absolute photoluminescence measurements with external quantum efficiencies ∼5% in complete cells. In addition, we find exceptionally long lifetimes...
Abstract Solar cells based on kesterite‐type Cu 2 ZnSnS 4 (CZTS) were fabricated molybdenum coated soda lime glass by evaporation using ZnS, Sn, Cu, and S sources. The coevaporation process was performed at a nominal substrate temperature of 550°C sulfur partial pressure 2–3 × 10 −3 Pa leading to polycrystalline CZTS thin films with promising electronic properties. absorber layers grown copper‐rich, requiring KCN etch step remove excess copper sulfide. compositional ratios as determined...
Identification of electronic processes at buried interfaces charge-selective contacts is crucial for photovoltaic and photocatalysis research. Here, transient surface photovoltage (SPV) used to study the passivation different hole-selective carbazole-based SAMs. It shown that SPV photoluminescence provide complementary information on charge transfer kinetics trapping/de-trapping mechanisms, trap-assisted non-radiative recombination losses originate from electron trapping SAM-modified...
A series of Cu(In,Ga)Se2 (CIGS) thin film solar cells with differently prepared heterojunctions has been investigated by admittance spectroscopy, capacitance-voltage (CV) profiling, and temperature dependent current-voltage (IVT) measurements. The devices different CdS buffer layer thicknesses, an In2S3 or a Schottky barrier junction, all show the characteristic step at shallow energies between 40 160 meV, which often referred to as N1 defect. No correlation thickness capacitance is found....
In the quest for better solar panels, we continue to refine our understanding of physics photovoltaic absorbers, such as hybrid metal-organic perovskites. By scrutinizing photoluminescence transients, authors explain how determine fundamental semiconductor properties and estimate potential open-circuit voltage perovskite thin films. Additionally, they highlight impacts photon recycling, doping, bulk surface recombination charge carriers on device performance.
Abstract Large datasets are now ubiquitous as technology enables higher-throughput experiments, but rarely can a research field truly benefit from the data generated due to inconsistent formatting, undocumented storage or improper dissemination. Here we extract all meaningful device peer-reviewed papers on metal-halide perovskite solar cells published so far and make them available in database. We collect over 42,400 photovoltaic devices with up 100 parameters per device. then develop...
Abstract Nanocrystal‐based Cu 2 Zn(Sn y Ge 1‐y )(S x Se 4‐x ) (CZTGeSSe) thin‐film solar cell absorbers with tunable band gap have been prepared. Maximum solar‐conversion total area efficiencies of up to 9.4% are achieved a content 30 at.%. Improved performance compared similarly processed films ZnSn(S (CZTSSe, 8.4% efficiency) is through controlling loss from the bulk absorber film during high‐temperature selenization treatment, although some surface still observed following this step....
Perovskite-based tandem solar cells can increase the power conversion efficiency (PCE) of conventional single-junction photovoltaic devices. Here, we present monolithic perovskite/CIGSe with a perovskite top cell fabricated directly on an as-grown, rough CIGSe bottom cell. To prevent potential shunting due to surface, thin NiOx layer is conformally deposited via atomic deposition front contact The performance further improved by additional polymer PTAA at NiOx/perovskite interface. This hole...
Tuning the energy levels of halide perovskite by controlling deposition dipolar self-assembled monolayers.
Abstract Perovskite semiconductors are an attractive option to overcome the limitations of established silicon based photovoltaic (PV) technologies due their exceptional opto‐electronic properties and successful integration into multijunction cells. However, performance single‐ cells is largely limited by significant nonradiative recombination at perovskite/organic electron transport layer junctions. In this work, cause interfacial perovskite/C 60 interface revealed via a combination...
Halide perovskites are a strong candidate for the next generation of photovoltaics. Chemical doping halide is an established strategy to prepare highest efficiency and most stable perovskite-based solar cells. In this study, we unveil mechanism using series alkaline earth metals. We find that low levels enable incorporation dopant within perovskite lattice, whereas high concentrations induce surface segregation. The threshold from regime correlates size element. show results in more n-type...
An approach is proposed to predict the impact of point defects on solar cell performance.
Abstract Understanding carrier loss mechanisms at microscopic regions is imperative for the development of high-performance polycrystalline inorganic thin-film solar cells. Despite progress achieved kesterite, a promising environmentally benign and earth-abundant photovoltaic material, their impact on device performance remain largely unknown. Herein, we unveil these in state-of-the-art Cu 2 ZnSnSe 4 (CZTSe) cells using framework that integrates multiple macroscopic characterizations with...
Abstract The next technological step in the exploration of metal‐halide perovskite solar cells is demonstration larger‐area device prototypes under outdoor operating conditions. authors here demonstrate that when slot‐die coating halide layers on large areas, ribbing effects may occur but can be prevented by adjusting precursor ink's rheological properties. For formamidinium lead triiodide (FAPbI 3 ) inks based 2‐methoxyethanol, ink viscosity adjusted adding acetonitrile (ACN) as a...
We demonstrate coherent nonlinear-optical control of excitons in a pair quantum dots (QDs) coupled via dipolar interaction. The single-exciton population the first QD is controlled by resonant picosecond excitation, giving rise to Rabi oscillations. As result, exciton transition second spectrally shifted and concomitant oscillations are observed. identify coupling between permanent excitonic dipole moments as dominant interaction mechanism, whereas quasiresonant (Förster) energy transfer...
The electronic structure of the CdS/Cu2ZnSnS4 (CZTS) heterojunction was investigated by direct and inverse photoemission. effects a KCN etch CZTS absorber prior to CdS deposition on band alignment at respective interface were studied. We find “cliff”-like conduction offset CdS/CZTS independent pretreatment significant etch-induced enhancement energetic barrier for charge carrier recombination across interface.
Thin film solar cells with Al/ITO/ZnO/CdS/CZTSSe/Mo‐glass structure are fabricated employing a fast and low‐cost preparation procedure using an aqueous ink deposited by nonpyrolytic spray, followed high temperature crystallization selenization steps. Capacitance–voltage measurements on previously reported devices >8% efficiency under 1 sun irradiation show charge carrier density of the order 10 17 cm −3 . Moreover, admittance spectroscopy indicates presence mid‐bandgap defects that...
Abstract The performance of many emerging compound semiconductors for thin‐film solar cells is considerably lower than the Shockley–Queisser limit, and one main reasons this presence various deleterious defects. A partial or complete substitution cations presents a viable strategy to alter characteristics detrimental defects defect clusters. Particularly, it hypothesized that double cation could be feasible mitigate negative effects different types In study, on pure‐sulfide Cu 2 ZnSnS 4...