Figure 1

(a) Relative elemental ratio of S/(S + Se) and (b) bandgap energy of solCIGS and K-solCIGS thin films; modified with permission from ref 14, Copyright 2020, WILEY–VCH. The gray colored areas show the minimum bandgap (Eg,min) region. (c) Optical absorption coefficient (α) spectra of solCIGS and K-solCIGS thin films.