Tailoring the properties of CZTS thin films through cation substitution and thermal annealing

Abstract

Pure sulfide kesterite (Cu2ZnSnS4 or CZTS) is a promising absorber material for next-generation photovoltaic (PV) technologies, especially for tandem and indoor applications. These quaternary chalcogenides offer tunable optoelectronic properties, an earth-abundant elemental composition, low cost, and high chemical stability [1]. However, the intrinsic bandgap of CZTS (≈1.5 eV) is suboptimal for tandem and indoor PV applications, which require a wider bandgap in the range of 1.65-1.9 eV. Alloying strategies based on cation substitution provide a flexible approach for engineering the structural, morphological, and optoelectronic properties. In particular, combining Ag alloying with alkaline metal incorporation enables effective tuning of these properties, offering a promising route for bandgap widening and absorber optimization.