Numerical modeling of ultra-thin CuSbS2 heterojunction solar cell with TiO2 electron transport and CuAlO2:Mg BSF layers

Abstract

The ternary chalcostibite copper antimony sulfide (CuSbS2) system, with its very high optical absorption coefficient, low-cost, vacuum-free fabrication techniques, and earth-abundant elements, is a rising candidate as solar absorber material for ultrathin film solar cells. However, due to the Schottky barrier formed at the back-contact and high carrier recombination at the CuSbS2/CdS interface, the efficiency of conventional CuSbS2/CdS heterojunction solar cell is very poor. This article proposes titanium dioxide (TiO2) as an alternative to CdS layer for the CuSbS2-based thin film solar cells (TFSCs). Using TiO2, CuSbS2, and Mg-doped CuAlO2 (CuAlO2:Mg) as an electron transport layer (ETL), absorber layer, and back-surface field (BSF) layer, respectively, a novel (Al/ITO/n-TiO2/p-CuSbS2/p+-CuAlO2:Mg/Au)-based npp+ heterojunction solar cell has been designed and simulated by SCAPS-1D solar cell simulator. The effects of integrating the CuAlO2:Mg BSF layer on the PV responses of the CuSbS2-based heterojunction solar cell in terms of the built-in potential and the back-contact carrier recombination have been studied. In addition, an investigation on the influences of various device parameters viz. carrier concentration and thickness of each layer, back-contact metal work function, shunt and series resistance, and working temperature have been carried out systematically. The results are analyzed in correlation with the PV parameters of the device to optimize the efficiency of the proposed solar cell. The optimized CuSbS2-based solar cell shows good performance stability at high temperature, with a maximum efficiency of 23.05% (Voc = 969 mV, Jsc= 34.61 mA/cm2, FF = 68.71%).