The effect of post-annealing on the performance of the Cu2 ZnSnS4 solar cells

Abstract Cu 2 ZnSnS 4 (CZTS) solar cells commonly undergo post-annealing treatments to enhance their performance. Yet, multiple concurrent effects, including Cu-Zn disorder, Na diffusion from the back contact, CZTS grain boundary passivation, and elemental inter-diffusion at the CdS/CZTS interface, can occur simultaneously during post-annealing, making it challenging to isolate their specific influence on device performance. To address this complexity, we have utilized fully Cu-Zn-disordered CZTS absorbers to eliminate the influence of Cu-Zn disorder in this work. Post-annealing experiments conducted at 120 to 300 0 C under nitrogen and air atmospheres aim to decouple and assess the impact of different annealing conditions on CZTS solar cell performance. Our findings suggest that the optimal post-annealing might be a combined effect of two distinct processes: CZTS absorber surface passivation occurring at 3250 C and CdS crystallization at 225 0 C. Hence, the improvement in device performance could result from multiple concurrent mechanisms occurring at different temperatures.