Towards high-efficiency cztse solar cells through the optimization of the p-MoSe2 interfacial layer

Abstract

This paper reports the impact of the p-MoSe2 transition metal dichalcogenide as an interfacial layer between the CZTSe absorber and Mo back contact in the CZTSe solar cells. Here, the solar cell capacitance simulator (SCAPS-1D) is employed. The I-V characteristic demonstrated a higher slope in comparison to CZTSe solar cell without considering the interfacial layer. The results show that the p-MoSe2 layer benefits the CZTSe/Mo hetero contact by mediating the quasi-ohmic back contact of the CZTSe solar cell. Accordingly, the conversion efficiency improves from 16.17 % to 23.47 %. To investigate the effect of the p-MoSe2 layer, various performance parameters such as open-circuit voltage (Voc), short circuit current (Jsc), fill factor FF, and efficiency η were explored at a wide range of thicknesses, bandgap energies, and the carrier concentration. The results revealed that a thickness of the interfacial layer less than 70 nm would cause deterioration of overall cell performance. This is because a low thickness of p-MoSe2 creates high barriers at the CZTS/p-MoSe2 and p-MoSe2/Mo interfaces, which impedes the drift process of photogenerated holes. Additionally, increasing the acceptor carrier concentration doping (NA) above 1017 cm-3 results in an improved cell performance due to the enhanced band alignment at the back contact. The obtained values of the Voc and Jsc are 0.74 V and 42.6 mA/cm2, respectively.