![]() Siebentritt, Susanne ![]() ![]() in Science China: Physics, Mechanics and Astronomy (2022) ![]() Siebentritt, Susanne ![]() ![]() in Faraday Discussions (2022) Absolute photoluminescence measurements present a tool to predict the quality of photovoltaic absorber materials before finishing the solar cells. Quasi Fermi level splitting predicts the maximal open ... [more ▼] Absolute photoluminescence measurements present a tool to predict the quality of photovoltaic absorber materials before finishing the solar cells. Quasi Fermi level splitting predicts the maximal open circuit voltage. However, various methods to extract quasi Fermi level splitting are plagued by systematic errors in the range of 10–20 meV. It is important to differentiate between the radiative loss and the shift of the emission maximum. They are not the same and when using the emission maximum as the “radiative” band gap to extract the quasi Fermi level splitting from the radiative efficiency, the quasi Fermi level splitting is 10 to 40 meV too low for a typical broadening of the emission spectrum. However, radiative efficiency presents an ideal tool to compare different materials without determining the quasi Fermi level splitting. For comparison with the open circuit voltage, a fit of the high energy slope to generalised Planck’s law gives more reliable results if the fitted temperature, i.e. the slope of the high energy part, is close to the actual measurement temperature. Generalised Planck’s law also allows the extraction of a non-absolute absorptance spectrum, which enables a comparison between the emission maximum energy and the absorption edge. We discuss the errors and the indications when they are negligible and when not. [less ▲] Detailed reference viewed: 60 (12 UL)![]() Ramirez Sanchez, Omar ![]() ![]() ![]() in APL Materials (2022) ![]() Wang, Taowen ![]() ![]() ![]() in Adv. Energy Mater (2022) ![]() Sood, Mohit ![]() ![]() in Progress in Photovoltaics (2021) Interface recombination in a complex multilayered thin-film solar structure causes a disparity between the internal open-circuit voltage (VOC,in), measured by photoluminescence, and the external open ... [more ▼] Interface recombination in a complex multilayered thin-film solar structure causes a disparity between the internal open-circuit voltage (VOC,in), measured by photoluminescence, and the external open-circuit voltage (VOC,ex), that is, a VOC deficit. Aspirations to reach higher VOC,ex values require a comprehensive knowledge of the connection between VOC deficit and interface recombination. Here, a near-surface defect model is developed for copper indium di-selenide solar cells grown under Cu-excess conditions. These cell show the typical signatures of interface recombination: a strong disparity between VOC,in and VOC,ex, and extrapolation of the temperature dependent q·VOC,ex to a value below the bandgap energy. Yet, these cells do not suffer from reduced interface bandgap or from Fermi-level pinning. The model presented is based on experimental analysis of admittance and deep-level transient spectroscopy, which show the signature of an acceptor defect. Numerical simulations using the near-surface defects model show the signatures of interface recombination without the need for a reduced interface bandgap or Fermi-level pinning. These findings demonstrate that the VOC,in measurements alone can be inconclusive and might conceal the information on interface recombination pathways, establishing the need for complementary techniques like temperature dependent current–voltage measurements to identify the cause of interface recombination in the devices. [less ▲] Detailed reference viewed: 66 (8 UL)![]() Shukla, Sudhanshu ![]() ![]() ![]() in Physical Review Materials (2021), 5 Detailed reference viewed: 130 (7 UL)![]() Weiss, Thomas ![]() ![]() ![]() in Solar RRL (2021) Detailed reference viewed: 118 (6 UL)![]() Wolter, Max ![]() in Progress in Photovoltaics (2021) Detailed reference viewed: 82 (0 UL)![]() Siebentritt, Susanne ![]() ![]() ![]() in JPhys Materials (2021) Detailed reference viewed: 62 (3 UL)![]() Weiss, Thomas ![]() ![]() ![]() in Physical Review Applied (2020), 14 Detailed reference viewed: 142 (11 UL)![]() Siebentritt, Susanne ![]() in Advanced Energy Materials (2020) Detailed reference viewed: 129 (6 UL)![]() Arnou, Panagiota ![]() ![]() ![]() in RSC Advances (2020) Detailed reference viewed: 140 (11 UL)![]() Weiss, Thomas ![]() in Scientific Reports (2019), 9 The knowledge of minority carrier lifetime of a semiconductor is important for the assessment of its quality and design of electronic devices. Time-resolved photoluminescence (TRPL) measurements offer the ... [more ▼] The knowledge of minority carrier lifetime of a semiconductor is important for the assessment of its quality and design of electronic devices. Time-resolved photoluminescence (TRPL) measurements offer the possibility to extract effective lifetimes in the nanosecond range. However, it is difficult to discriminate between surface and bulk recombination and consequently the bulk properties of the semiconductor cannot be estimated reliably. Here we present an approach to constrain systematically the bulk and surface recombination parameters in semiconducting layers and reduces to finding the roots of a mathematical function. This method disentangles the bulk and surface recombination based on TRPL decay times of samples with different surface preparations. The technique is exemplarily applied to a CuInSe2 and a back-graded Cu(In,Ga)Se2 compound semiconductor, and upper and lower bounds for the recombination parameters and the mobility are obtained. Sets of calculated parameters are extracted and used as input for simulations of photoluminescence transients, yielding a good match to experimental data and validating the effectiveness of the methodology. A script for the simulation of TRPL transients is provided. [less ▲] Detailed reference viewed: 39 (0 UL)![]() Weiss, Thomas ![]() ![]() in Science and Technology of Advanced Materials (2019), 20 Detailed reference viewed: 166 (3 UL)![]() Werner, Florian ![]() ![]() ![]() in Progress in Photovoltaics (2018) Detailed reference viewed: 213 (5 UL)![]() Rey, Germain ![]() ![]() ![]() in Thin Solid Films (2016), 633 Low temperature post-deposition treatment of Cu2ZnSnSe4 with NaF and KF significantly improved the solar cell efficiency (from 6.4% to 7.8% and 7.7% on average, respectively) due to enhanced fill factor ... [more ▼] Low temperature post-deposition treatment of Cu2ZnSnSe4 with NaF and KF significantly improved the solar cell efficiency (from 6.4% to 7.8% and 7.7% on average, respectively) due to enhanced fill factor (from 0.58 to 0.61 and 0.62), open-circuit voltage (Voc) (from 314 mV to 337 mV and 325 mV) and short-circuit current density (from 35.3 mA⋅cm −2 to 38.3 mA⋅cm −2 and 38.6 mA⋅cm −2). Voc improvement was higher for solar cells with NaF treatment due to an increase in radiative efficiency at room temperature and shallower defect activation energy as determined by photoluminescence (PL) and temperature dependent admittance spectroscopy, respectively. In the case of KF treatment, red-shift of the PL, higher band tail density of state and donor activation energy deeper in the band gap were limiting further improvement of the Voc compared to NaF treatment. [less ▲] Detailed reference viewed: 220 (10 UL)![]() Weiss, Thomas ![]() ![]() ![]() in Journal of Applied Physics (2016), 120 Detailed reference viewed: 209 (10 UL)![]() Rey, Germain ![]() ![]() ![]() in Solar Energy Materials and Solar Cells (2016), 151 Detailed reference viewed: 267 (18 UL)![]() Weiss, Thomas ![]() Doctoral thesis (2015) Detailed reference viewed: 206 (18 UL) |
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