Effect of Post-annealing on the Solar Cell Performance of Cu2ZnSnS4 Thin Film Prepared by Sulfurization of Stacked Metal Precursor with H2S Gas

The influence of post-annealing on the solar cell performance of Cu
₂
ZnSnS
₄
(CZTS) thin film prepared by sulfurization of Zn/(Cu,Sn) metal precursor with H
₂
S gas was investigated. Two-step annealing process at 450°C and then at 550°C was adopted for the sulfurization of the stacked precursor in the mixed N
₂
+H
₂
S atmosphere. The post-annealing was performed at 300°C in air after the deposition of CdS buffer layer and Ni/Al grid. In comparison to the CZTS solar cell prepared without post-annealing showing lower efficiency of 4.30%, improved solar cell efficiency of 6.02% with increased Voc (590 mV) and FF (56.2%) was observed for the CZTS solar cell prepared with post-annealing. By the analysis of Voc as a function of temperature and frequency-dependent carrier concentration, the improved cell efficiency was believed to be due to the reduced absorber/buffer interface recombination and bulk defects in CZTS.