A PL and PLE Study of High Cu Content Cu2ZnSnSe4 Films on Mo/Glass and Solar Cells

Sulimov, M. A., Yakushev, M. V., Forbes, Ian, Prieto, J. M., Mudryi, A. V., Krustok, Ju., Edwards, P. R. and Martin, R. W. (2019) A PL and PLE Study of High Cu Content Cu2ZnSnSe4 Films on Mo/Glass and Solar Cells. Physics of the Solid State, 61 (5). pp. 908-917. ISSN 1063-7834

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Abstract

Cu2ZnSnSe4 (CZTSe) is amongst leading candidates for the absorber layer in sustainable solar cells. We examine CZTSe thin films with [Cu]/[Zn + Sn] of 0.99 and [Zn]/[Sn] of 1.07, deposited on Mo/glass substrates, and solar cells fabricated from these films. The bandgap (Eg) of the as deposited films and solar cells was examined by photoluminescence excitation (PLE) whereas the temperature and excitation intensity dependence of photoluminescence (PL) spectra was used to examine the nature of radiative recombination. The 6 K PL spectra of CZTSe/Mo exhibit an intense broad and asymmetrical band P1 at 0.822 eV and a lower intensity band P2 at 0.93 eV. The shape of this band, high rates of blue shift with excitation intensity rise ( j-shift) j(P1) = 14 meV and j(P2) = 8 meV per decade, and red shifts of both bands with increasing temperature suggest that both bands are associated with valence band tails due to potential fluctuations caused by high populations of charged defects. The mean depth of such fluctuation γ of 24 meV was estimated from the low energy side of P1. Device processing increased Eg, blue shifted P1, decreased its width, j-shift and the mean depth of potential fluctuations. These can be due to the annealing and/or can partly be related to KCN etching and the chemical effect of Cd, from CdS replacing copper at the CdS–CZTSe interface layer. Processing induced a new broad band P3 at 1.3 eV (quenching with Ea = 200 meV). We attributed P3 to defects in the CdS layer.

Item Type:	Article
Subjects:	F200 Materials Science F300 Physics F500 Astronomy
Department:	Faculties > Engineering and Environment > Mathematics, Physics and Electrical Engineering
Depositing User:	Elena Carlaw
Date Deposited:	08 Jul 2019 14:40
Last Modified:	10 Oct 2019 17:19
URI:	http://nrl.northumbria.ac.uk/id/eprint/39898

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