Regulation of Zn/Sn ratio in kesterite absorbers to boost 10% efficiency of Cu2ZnSn(S, Se)4 solar cells |
(color online) (a) Normalized Raman spectra for R0–R4 CZTSSe absorber films. (b) Zoomed-in Raman spectra at the wave number from 220 cm−1 to 280 cm−1. |