Impressive self-healing phenomenon of Cu₂ZnSn(S, Se)₄ solar cells

A study of the self-healing phenomenon of Cu₂ZnSn(S, Se)₄ (CZTSSe) solar cells has shown more than 10% enhancement in cell performance after storage at room temperature for a week, with a significant improvement in the open-circuit photovoltage (V_oc) and fill factor (FF). In addition, up to 10.45% power conversion efficiency (PCE) has been achieved. No obvious change in crystallinity, crystal phase, optical absorption or elemental distribution in the CZTSSe films was detected on examining the x-ray diffraction (XRD) pattern, Raman spectrum, ultraviolet-visible (UV-Vis), and TOF-SIMS. Further investigations on the charge carrier concentration, charge radiative recombination, and band structure suggest that the enhancement in PCE stems mainly from a reduction in deep defects of the CZTSSe semiconductor film.