Control of the phase evolution of kesterite by tuning of the selenium partial pressure for solar cells with 13.8% certified efficiency

Phase evolution during the selenization is crucial for high-quality kesterite Cu2ZnSn(S, Se)4 (CZTSSe) absorbers and efficient solar cells. Herein, we regulate kinetic process of phase from Cu+-Sn4+-MOE (MOE: 2-methoxyethanol) system by precisely controlling positive chamber pressure. We found that, at heating-up stage, Se vapor concentration intentionally suppressed in low-temperature region, which effectively reduces collision probability between CZTS atoms, thus remarkably inhibiting formation secondary phases on surface multiple-step processes. This strategy enables to start relatively higher temperature thereby leading high crystalline quality CZTSSe absorber with fewer defects, corresponding cell can present 14.1% efficiency (total area), highest result so far. work provides important insights into mechanism explores a new way regulation simplify path