Impact of the selenisation temperature on the structural and optical properties of CZTSe absorbers

J. Márquez-Prieto, M. V. Yakushev, I. Forbes, J. Krustok, P. R. Edwards, V. D. Zhivulko, O. M. Borodavchenko, A. V. Mudryi, M. Dimitrievska, V. Izquierdo-Roca, N. Pearsall, R. W. Martin

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Abstract

We present structural and optical spectroscopy studies of thin films of Cu2ZnSnSe4 (CZTSe) with strong copper deficiency deposited on Mo/Glass substrates and selenised at 450, 500 or 550 °C. Solar cells fabricated from these films demonstrated efficiencies up to 7.4% for selenisation at 500 °C. Structural analysis based on X-ray diffraction and Raman spectroscopy revealed the presence of SnSe2 in the film selenised at 450 °C but not detected in the films selenised at higher temperatures. A progressive decrease of the Sn and Se content was observed as the selenisation temperature increased. Photoluminescence excitation was used to determine the bandgaps at 4.2 K. Detailed measurements of the temperature and excitation intensity dependencies of the photoluminescence spectra allow the recombination mechanisms of the observed emission bands to be identified as band-to-impurity and band-to-band transitions, and their evolution with selenisation temperature changes to be analysed. The strongest band-to-band transition is recorded in the PL spectra of the film selenised at 500 °C and can be observed from 6 K to room temperature. The compositional and structural changes in the films and their influence on the optoelectronic properties of CZTSe and solar cells are discussed.
Original languageEnglish
Pages (from-to)42-50
Number of pages9
JournalSolar Energy Materials and Solar Cells
Volume152
Early online date6 Apr 2016
DOIs
Publication statusPublished - 31 Aug 2016

Keywords

  • Cu2ZnSnSe4
  • selenisation
  • optical spectroscopy
  • structure

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