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

ABSTRACT

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 η 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 10¹⁶ 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/cm², 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 Ω to 5 Ω.

KEYWORDS:

• CZTS
• p-mos₂
• tmdc
• thin-film solar cell
• scaps

Acknowledgments

We gratefully thank Marc Burgelman and his colleagues at the University of Gent, Belgium, for providing the SCAPS-1D software package used in all simulations reported in this paper.

Disclosure statement

No potential conflict of interest was reported by the author(s).