Influence of order-disorder in Cu2ZnSnS4 powders on the performance of monograin layer solar cells

Abstract In this study the influence of low-temperature structural ordering in absorber material to the performance of Cu 2 ZnSnS 4 (CZTS) monograin layer (MGL) solar cells was investigated. The shift of peak position in low temperature and room temperature photoluminescence measurements was used to estimate the Cu-Zn disorder level in CZTS monograin powders. The degree of Cu-Zn ordering was changed by using different cooling times after annealing CZTS powders in S atmosphere at 740 °C and by additional annealing at temperatures below critical temperature ( T c ~ 260 °C) for different time periods. Current-voltage measurements revealed that the low-temperature thermal treatments resulting in increased ordering of CZTS absorber material had significant impact on the MGL solar cell characteristics, mostly, the values of open circuit voltage ( V oc ) were increased. The highest V oc of 784 mV was measured for the solar cell based on the powder that was cooled from 740 °C to room temperature for 5 min followed by annealing at 150 °C for 24 h. Optimal conditions for low-temperature annealing to improve CZTS MGL solar cells' performance were found to be 4 h at 150 °C. These improvements resulted in CZTS MGL solar cell power conversion efficiency of 9.1% (active area).