Electronic properties of the Cu 2ZnSn(Se,S) 4 absorber layer in solar cells as revealed by admittance spectroscopy and related methods
Admittance spectra and drive-level-capacitance profiles of several high performance Cu 2ZnSn(Se,S) 4 (CZTSSe) solar cells with bandgap ∼1.0-1.5 eV are reported. In contrast to the case for Cu(In,Ga)(S,Se) 2, the CZTSSe capacitance spectra exhibit a dielectric freeze out to the geometric capacitance plateau at moderately low frequencies and intermediate temperatures (120-200 K). These spectra reveal important information regarding the bulk properties of the CZTSSe films, such as the dielectric constant and a dominant acceptor with energy level of 0.13-0.2 eV depending on the bandgap. This deep acceptor leads to a carrier freeze out effect that quenches the CZTSSe fill factor and efficiency at low temperatures. © 2012 American Institute of Physics.
Gunawan, O; Gokmen, T; Warren, CW; Cohen, JD; Todorov, TK; Barkhouse, DAR; Bag, S; Tang, J; Shin, B; Mitzi, DB
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