Performance evaluation of WS2 as buffer and Sb2S3 as HTL in CZTS solar
cell by numerical simulation
Abstract
This study reports on performance enhancement in a solar cell
introducing Sb2S3 as hole transport layer (HTL)along WS2 as buffer
layer. We have investigated photovoltaic (PV) characteristics by
utilizing SCAPS-1D. A comparative observation on PV performances of
conventional CZTS/CdS with proposed CZTS/WS2 and Ni/Sb2S3/CZTS/WS2
/FTO/Al solar cells is presented. It is revealed that “spike like”
band structure at CZTS/WS2 interface having smaller conduction band
offset makes it potential alternative to commonly used CdS buffer. This
study also evaluates that Sb2S3 as an HTL proposed at back of CZTS
enhances performances by reducing carrier recombination at back
interface with appropriate band alignment. The impacts of thickness,
carrier concentration of different layers, and bulk defect density in
CZTS as well as defects at interfaces on performances are analyzed. The
influences of temperature, work function as well as cell resistances are
also explored. Optimum absorber thickness of 1.0 µm along doping of 10
17 cm-3 is selected. A maximum efficiency of 30.63% is achieved for the
optimized CZTS cell. Therefore, these results suggest that Sb2S3 as
HTLand WS2 as buffer layer can be employed effectively to develop highly
efficient and low-cost CZTS solar cells.