Effects of Transition Metal Dichalcogenide Molybdenum Disulfide Layer Formation in Copper–Zinc–Tin–Sulfur Solar Cells from Numerical Analysis

Abstract

This study demonstrates the effects of transition metal dichalcogenide, MoS 2 layer formation in between the copper–zinc–tin–sulphide (CZTS) absorber layer and Mo back contact from theoretical study and numerical modeling. The objective of this study is to elucidate the effects of n or p type MoS 2 on the overall CZTS solar cell performance. Energy band line-up of Mo/MoS 2 /CZTS interface is analyzed to elucidate the interface properties. It is found out that p-MoS 2 layer in CZTS solar cell induces the same adventitious effect as p-MoSe 2 in CIGS solar cell. However, n-MoS 2 layer has detrimental effect on the CZTS solar cell by creating an additional back contact diode with p-CZTS layer and an ohmic contact with Mo layer. Thickness, bandgap energy and carrier concentration of n-MoS 2 all have been varied in the numerical simulation to observe its effects on the cell performance parameters. The results from numerical simulation show that MoS 2 layer as thin as 50 nm is sufficient enough to induce adverse effect on the solar cell performance. This could be caused by the increase in series resistance of the solar cell as n-type MoS 2 would inhibit hole current into Mo back contact due to the hole barrier between n-type MoS 2 and Mo back contact. The increase in MoS 2 bandgap and carrier concentration also results in detrimental effect to the performance of the cell mainly due to the possibility of electrons to drift towards the back contact and recombine.