Towards high-efficiency CZTS solar cells via p-MoS2 interfacial layer optimisation

This paper discusses the impact of the p-MoS2 transition metal dichalcogenide as an interfacial layer between the CZTS absorber and Mo back contact in the CZTS based solar cell. The study was performed using SCAPS-1D numerical simulation. The I-V characteristic demonstrated a higher slope than CZTS solar cells without considering the interfacial layer. The results verified that the p-MoS2 layer beneficially on the CZTS/Mo hetero-contact mediating an ohmic contact. Accordingly, the conversion efficiency improves from 12.14% to 16.71%. To evaluate the role of the p-MoS2 layer, various performance parameters such as open-circuit voltage (V-oc), short circuit current (J(sc)), fill factor FF, and efficiency eta were explored versus thicknesses, bandgap energies, and the acceptor carrier concentration (N-A). The results show that a thickness of the interfacial layer of less than 200 nm could cause deterioration of the overall cell performance, mainly due to created high barriers at the CZTS/p-MoS2 and p-MoS2/Mo interfaces, at low thicknesses, which impedes the drift of photogenerated holes. Additionally, increasing the N-A above 10(16) cm(-3) improves the cell performance, owing to the favourable band alignment at the back contact. Values obtained for V-oc and J(sc) are 0.88 V and 25.5 mA/cm(2), respectively. Moreover, the effect of series resistance R-s on CZTS solar cells was investigated. The efficiency decreases from 12.84% to 9.69% when the R-s correspondingly increases from 0 omega to 5 omega.