Susanne Siebentritt

University of Luxembourg

Author Statistics

Papers

Citation

H-Index

i-10 index

Research Trends

Author Order

Document Type

Co-Authors

Alex Redinger

University of Luxembourg

Michele Melchiorre

University of Luxembourg

Thomas Paul Weiss

University of Luxembourg

Phillip J. Dale

University of Luxembourg

Martha Ch. Lux‐Steiner

Freie Universität Berlin

Mohit Sood

University of Luxembourg

Levent Gütay

Carl von Ossietzky Universität Oldenburg

Marina Mousel

University of Luxembourg

Florian Werner

University of Luxembourg

Torsten Schwarz

Max-Planck-Institut für Nachhaltige Materialien

Cooperative Institutions

University of Luxembourg

135

Helmholtz-Zentrum Berlin für Materialien und Energie

New York University Press

Fraunhofer Institute for Telecommunications, Heinrich Hertz Institute

Centre National de la Recherche Scientifique

German Orient Foundation

University of Cambridge

Luxembourg Institute of Science and Technology

National Renewable Energy Laboratory

Technische Universität Berlin

Author Statistics

Papers

Citation

H-Index

i-10 index

Research Field

Excitation-intensity dependence of shallow and deep-level photoluminescence transitions in semiconductors

Journal of Applied Physics (2019)

Conrad Spindler Thomas Galvani Ludger Wirtz Germain Rey Susanne Siebentritt

Photoluminescence characterization of semiconductors is a powerful tool for studying shallow and deep defects. Excitation-intensity-dependent measurements at low temperatures are typically analyzed to distinguish between exciton and defect related transitions. We have extended existing models based on rate equations to include the contribution of deep defects. Generally, it is observed that the photoluminescence intensity IPL follows a power law IPL∝ϕk with the excitation intensity ϕ. We show that the exponent k takes on values of multiples of 1/2. The values depend on the availability of additional recombination channels. Defect levels can saturate at high enough excitation intensities, leading to one or several crossover points from one power law behavior to another. Power law exponents different from n/2 can result from the transition region between two limiting cases of linear power laws. Model functions for the analytical description of these transitional excitation dependencies are derived and the analysis is applied to chalcopyrite thin films and to numerical data. The saturation effects of defects by excess carriers as well as the influence of deep recombination centers can be extracted with the help of the presented model, which extends existing theories.

Saturation (graph theory)

Intensity

Exponent

Rate equation

Limiting

10.1063/1.5095235

Cite

Citations (57)

Investigations of Porphyrins and Aromatic Tetracarboxylic Acid Diimides for use in Photovoltaics

Molecular crystals and liquid crystals science technology. Section A, Molecular crystals and liquid crystals/Molecular crystals and liquid crystals science and technology. Section A, Molecular crystals and liquid crystals (1992)

Stefan Güster Susanne Siebentritt Jörg Elbe Lutz Kreienhoop Bernd Tennigkeit

Abstract Photovoltaic double layer cells of phorphyrinic and aromatic tetracarboxylic acid diimid compounds are presented. The photovoltaic characteristics photovoltage, short circuit current and efficiency are reported. In addition the physical characteristics of two model compounds of each class of substances are reported.

10.1080/10587259208047026

Cite

Citations (18)

Electrical barriers and their elimination by tuning (Zn,Mg)O composition in Cu(In,Ga)S2: Systematic approach to achieve over 14% power conversion efficiency

arXiv (Cornell University) (2022)

Mohit Sood Poorani Gnanasambandan Damilola Adeleye Sudhanshu Shukla Noureddine Adjeroud

Traditional CdS buffer layer in selenium-free Cu(In,Ga)S2 solar cells leads to reduced open-circuit voltage because of a negative conduction band offset at the Cu(In,Ga)S2/CdS interface. Reducing this loss necessitates the substitution of CdS by an alternative buffer layer. However, the substitute buffer layer may introduce electrical barriers in the device due to unfavorable band alignment at the other interfaces such as between buffer/ZnO i-layer. This study aims to reduce interface recombinations and eliminate electrical barriers in Cu(In,Ga)S2 solar cells using a combination of Zn1-xMgxO and Al-doped Zn1-xMgxO buffer and i-layer combination deposited using atomic layer deposition and magnetron sputtering, respectively. The devices prepared with these layers are characterized by current-voltage and photoluminescence measurements. Numerical simulations are performed to comprehend the influence of electrical barriers on the device characteristics. An optimal composition of Zn1 xMgxO x = 0.27 is identified for a suitable conduction band alignment with Cu(In,Ga)S2 with a bandgap of ~1.6 eV, suppressing interface recombination and avoiding barriers. Optimized buffer composition together with a suitable i-layer led to a device with 14 % efficiency and an open-circuit voltage of 943 mV. A comparison of optoelectronic measurements for devices prepared with ZnO and Al:(Zn,Mg)O shows the necessity to replace the ZnO i-layer with Al:(Zn,Mg)O i-layer for a high-efficiency device.

Buffer (optical fiber)

Open-circuit voltage

Band offset

10.48550/arxiv.2202.10708

Cite

Citations (0)

How to use photoluminescence to improve your solar cells

Susanne Siebentritt

10.29363/nanoge.absogen.2020.008

Cite

Citations (0)

Influence of copper excess on the absorber quality of CuInSe2

Applied Physics Letters (2011)

Levent Gütay David Regesch Jes K. Larsen Yasuhiro Aida Valérie Deprédurand

The compositional dependence of the optoelectronic quality of CuInSe2 thin film absorbers is investigated on single- and poly-crystalline films with varying [Cu]/[In]-ratios. We quantify the quality of the absorbers by the splitting of quasi-Fermi levels, determined by spectral photoluminescence. This quantity determines the maximum achievable open circuit voltage by an absorber. Our results indicate a significant increase of this value for growth under Cu-excess, indicating a decrease of recombination losses. By comparison of the predicted achievable open circuit voltage and the actually measured ones of finished solar cells, we find a huge “un-utilized potential” for the Cu-rich devices.

Open-circuit voltage

10.1063/1.3648111

Cite

Citations (33)

CuIn(Se,Te)2 absorbers with bandgaps < 1 eV for bottom cells in tandem applications

arXiv (Cornell University) (2023)

Thomas Paul Weiss Mohit Sood Aline Vanderhaegen Susanne Siebentritt

Thin-film solar cells reach high efficiencies and have a low carbon footprint in production. Tandem solar cells have the potential to significantly increase the efficiency of this technology, where the bottom-cell is generally composed of a Cu(In,Ga)Se2 absorber layer with bandgaps around 1 eV or higher. Here, we investigate CuIn(Se1-xTex)2 absorber layers and solar cells with bandgaps below 1 eV, which will bring the benefit of an additional degree of freedom for designing current-matched 2-terminal tandem devices. We report that CuIn(Se1-xTex)2 thin films can be grown single phase by co-evaporation and that the bandgap can be reduced to the optimum range for a bottom cell (0.92 - 0.95 eV). From photoluminescence spectroscopy it is found that no additional non-radiative losses are introduced to the absorber. However, Voc losses occur in the final solar cell due to non-optimised interfaces. Nevertheless, a record device with 9 % power conversion efficiency is demonstrated with a bandgap of 0.96 eV and x=0.15. Interface recombination is identified as a major recombination channel for larger Te contents. Thus, further efficiency improvements are anticipated for improved absorber/buffer interfaces.

Tandem

10.48550/arxiv.2308.16103

Cite

Citations (0)

Vacuum‐Healing of Grain Boundaries in Sodium‐Doped CuInSe₂ Solar Cell Absorbers

Advanced Energy Materials (2023)

Finn Babbe Nicoleta Nicoara Harvey Guthrey Nathalie Valle Omar Ramírez

Abstract Alkali metal doping and grain boundaries (GB) have been at the center of attention within the Cu(In,Ga)(S,Se) 2 photovoltaics community for years. This study provides the first experimental evidence that the GB of sodium‐doped CuInSe 2 thin films may undertake reversible oxidation even at room temperature, whereas undoped films may not. The findings are corroborated by cathodoluminescence imaging, secondary ion mass spectrometry, and Kelvin probe force microscopy on air‐exposed films subsequently subject to vacuum. A thermochemical assessment identifies the likely solid–gas equilibria involved. These reactions open new research questions with respect to the beneficial role played by alkali metal dopants in chalcopyrite solar cells and may steer the community toward new breakthroughs.

Cathodoluminescence

10.1002/aenm.202204183

Cite

Citations (11)

硫化インジウムバッファ層を有し,一部工程に湿式化学処理を施したCu(In,Ga)(S,Se) 2 ベース太陽電池のアニーリング挙動の比較研究

Journal of Applied Physics (2015)

C Hoenes J Hackenberg S Zweigart André Wachau F Hergert

Source

Cite

Citations (0)

Time-resolved photoluminescence on double graded Cu(In,Ga)Se₂ – Impact of front surface recombination and its temperature dependence

Science and Technology of Advanced Materials (2019)

Thomas Paul Weiss Romain Carron Max Hilaire Wolter Johannes Löckinger Enrico Avancini

Time-resolved photoluminescence (TRPL) is applied to determine an effective lifetime of minority charge carriers in semiconductors. Such effective lifetimes include recombination channels in the bulk as well as at the surfaces and interfaces of the device. In the case of Cu(In,Ga)Se2 absorbers used for solar cell applications, trapping of minority carriers has also been reported to impact the effective minority carrier lifetime. Trapping can be indicated by an increased temperature dependence of the experimentally determined photoluminescence decay time when compared to the temperature dependence of Shockley-Read-Hall (SRH) recombination alone and can lead to an overestimation of the minority carrier lifetime. Here, it is shown by technology computer-aided design (TCAD) simulations and by experiment that the intentional double-graded bandgap profile of high efficiency Cu(In,Ga)Se2 absorbers causes a temperature dependence of the PL decay time similar to trapping in case of a recombinative front surface. It is demonstrated that a passivated front surface results in a temperature dependence of the decay time that can be explained without minority carrier trapping and thus enables the assessment of the absorber quality by means of the minority carrier lifetime. Comparison with the absolute PL yield and the quasi-Fermi-level splitting (QFLS) corroborate the conclusion that the measured decay time corresponds to the bulk minority carrier lifetime of 250 ns for the double-graded CIGS absorber under investigation.

Carrier lifetime

Charge carrier

10.1080/14686996.2019.1586583

Cite

Citations (19)

Ultra-thin passivation layers in Cu(In,Ga)Se2 thin-film solar cells: full-area passivated front contacts and their impact on bulk doping

Scientific Reports (2020)

Florian Werner Boris Veith‐Wolf Michele Melchiorre Finn Babbe Jan Schmidt

Abstract In the search for highly transparent and non-toxic alternative front layers replacing state-of-the-art CdS in Cu(In,Ga)Se 2 thin-film solar cells, alternatives rarely exceed reference devices in terms of efficiency. Full-area ultra-thin aluminium oxide tunnelling layers do not require any contact patterning and thus overcome the main drawback of insulating passivation layers. Even a few monolayers of aluminium oxide can be deposited in a controlled manner by atomic layer deposition, they show excellent interface passivation properties, low absorption, and suitable current transport characteristics on test devices. Depositing a ZnO-based transparent front contact, however, results in extremely poor solar cell performance. The issue is not necessarily a low quality of the alternative front layer, but rather the intricate relation between front layer processing and electronic bulk properties in the absorber layer. We identify three challenges critical for the development of novel front passivation approaches: (i) both Cd and Zn impurities beneficially reduce the high native net dopant concentration in the space charge region, (ii) sputter deposition of ZnO damages the passivation layer resulting in increased interface recombination, (iii) thermal treatments of devices with ZnO layer result in substantial Zn diffusion, which can penetrate the full absorber thickness already at moderate temperatures.

Passivation

10.1038/s41598-020-64448-9

Cite

Citations (26)