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1,130 results on '"Yakushev, A. V."'

154. Mapping the Energetics of Defect States in Cu₂ZnSnS₄films and the Impact of Sb Doping

Author

Tiwari, Devendra, Yakushev, Michael V., Köhler, Tristan, Cattelan, Mattia, Fox, Neil, Martin, Robert W., Klenk, Reiner, and Fermin, David J.

Subjects
Physik (inkl. Astronomie)
Abstract

The sub-bandgap levels associated with defect states in Cu2ZnSnS4 (CZTS) thin films are investigated by correlating the temperature dependence of the absorber photoluminescence (PL) with the device admittance spectroscopy. CZTS thin films are prepared by thermolysis of molecular precursors incorporating chloride salts of the cations and thiourea. Na and Sb are introduced as dopants in the precursor layers to assess their impact on Cu/Zn and Sn site disorder, respectively. Systematic analysis of PL spectra as a function of excitation power and temperature show that radiative recombination is dominated by quasi-donor-acceptor pairs (QDAP) with a maximum between 1.03 and 1.18 eV. It is noteworthy that Sb doping leads to a transition from localized to delocalized QDAP. The activation energies obtained associated with QDAP emission closely correlate with the activation energies of the admittance responses in a temperature range between 150 K and room temperature in films with or without added dopants. Admittance data of CZTS films with no added dopants also have a strong contribution from a deeper state associated with Sn disorder. The ensemble of PL and admittance data, in addition to energy-filtered photoemission of electron microscopy (EF-PEEM), shows a detailed picture of the distribution of sub-bandgap states in CZTS and the impact of doping on their energetics and device performance.

Published
2022

169. Properties of arsenic–implanted Hg1-xCdxTe MBE films

Author

Izhnin Igor I., Voitsekhovskii Alexandr V., Korotaev Alexandr G., Fitsych Olena I., Bonchyk Oleksandr Yu., Savytskyy Hrygory V., Mynbaev Karim D., Varavin Vasilii S., Dvoretsky Sergey A., Yakushev Maxim V., Jakiela Rafal, and Trzyna Malgorzata

Subjects
Physics, QC1-999
Abstract

Defect structure of arsenic-implanted Hg1-xCdxTe films (x=0.23–0.30) grown with molecular-beam epitaxy on Si substrates was investigated with the use of optical methods and by studying the electrical properties of the films. The structural perfection of the films remained higher after implantation with more energetic arsenic ions (350 keV vs 190 keV). 100%-activation of implanted ions as a result of post-implantation annealing was achieved, as well as the effective removal of radiation-induced donor defects. In some samples, however, activation of acceptor-like defects not related to mercury vacancies as a result of annealing was observed, possibly related to the effect of the substrate.

Published
2017
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183. Effects of irradiation of ZnO/CdS/Cu2ZnSnSe4/Mo/glass solar cells by 10 MeV electrons on photoluminescence spectra

Author

Sulimov, M. A., Sarychev, M. N., Yakushev, M. V., Márquez-Prieto, J., Forbes, I., Ivanov, V. Y., Edwards, P. R., Mudryi, A. V., Krustok, J., Martin, R. W., Sulimov, M. A., Sarychev, M. N., Yakushev, M. V., Márquez-Prieto, J., Forbes, I., Ivanov, V. Y., Edwards, P. R., Mudryi, A. V., Krustok, J., and Martin, R. W.

Abstract

Solar cells with the structure ZnO/CdS/Cu2ZnSnSe4/Mo/glass were studied by photoluminescence (PL) before and after irradiation with a dose of 1.8 × 1015 cm−2 and then 5.4 × 1015 cm−2 of 10 MeV electrons carried out at 77 K in liquid nitrogen bath. The low temperature PL spectra before irradiation revealed two bands, a broad and asymmetrical dominant band at 0.94 eV from the CZTSe layer and a lower intensity high energy band (HEB) at 1.3 eV, generated by defects in the CdS buffer layer. Analysis of the excitation intensity and temperature dependencies suggested that the dominant band is free-to-bound (FB): the recombination of free electrons with holes localised at acceptors whose energy levels are affected by potential fluctuations of the valence band due to high concentrations of randomly distributed charged defects. Irradiation did not induce any new band in the examined spectral range (from 0.5 μm to 1.65 μm) but reduced the intensity of both bands in the PL spectra measured at 77 K without warming the cells. The higher the dose the greater was the reduction. After this the cells were warmed to 300 K and moved to a variable temperature cryostat to measure temperature dependencies of the PL spectra. After irradiation the red shift rate of the FB band with temperature rise was found to increase. Electrons displace atoms in the lattice creating primary defects: interstitials and vacancies. These defects recombine during and shortly after irradiation forming secondary defect complexes which work as deep non-radiative traps of charge carriers reducing the PL intensity and increasing the rate of the temperature red shift. Irradiation did not affect the mean depth of the band tails estimated from the shape of the low energy side of the dominant PL band. © 2020 Elsevier Ltd

Published
2021

184. Photoluminescence, Stimulated and Laser Emission in CuInSe2crystals

Author

Svitsiankou, I. E., Pavlovskii, V. N., Lutsenko, E. V., Yablonskii, G. P., Mudryi, A. V., Borodavchenko, O. M., Zhivulko, V. D., Martin, R. W., Yakushev, M. V., Svitsiankou, I. E., Pavlovskii, V. N., Lutsenko, E. V., Yablonskii, G. P., Mudryi, A. V., Borodavchenko, O. M., Zhivulko, V. D., Martin, R. W., and Yakushev, M. V.

Abstract

Excitonic quality CuInSe2 crystals were studied using low-temperature (10 K) photoluminescence (PL) excited by continuous wave and nanosecond pulsed lasers at power densities from 0.01 to 76 kW/cm2. Increasing the excitation power density level to 26 kW/cm2 resulted in the appearance of a stimulated emission SE-band in the PL spectra at 1.035 eV. Further increase in the excitation level to 39 kW/cm2 generated on the top of the SE band, a structure of equidistant sharp lines attributed to laser emission. © 2021 Author(s).

Published
2021

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