Influence of thiourea concentration during deposition of a CdS buffer layer on the electric properties of Cu2SnS3 solar cells

Abstract

The p–n interface state and depletion layer region of solar cells were investigated using electrochemical impedance spectroscopy (EIS) measurements to elucidate the effect of varying thiourea (TU) concentrations in chemical bath deposition (CBD) on the photovoltaic properties of Cu2SnS3 (CTS) solar cells. The photoconversion efficiency (PCE) increased as the TU concentration increased, peaking at 0.16 M and decreasing thereafter. Additionally, the constant phase element-p value, which is indicative of the p–n interface state in CTS solar cells, exhibited a similar trend to that of the PCE of CTS solar cells with increasing TU concentration. The decrease in the PCE was due to the electron recombination that occurred at the p–n interface of CTS solar cells with increasing TU concentrations. Therefore, to improve the PCE of the CTS solar cells, the TU concentration in CBD must be optimized because the p–n interface state is sensitive to changes in the growth conditions of CdS films. By studying the effects on the p–n interface state and depletion layer in CTS solar cells using EIS measurements, useful knowledge can be obtained to increase the PCE of all-sulfide-compound solar cells using n-type CdS films as well as CTS.