P-type to N-type conversion of Fe-doped Cu2BaSnS4

Abstract

In this study, we report p-type to n-type conversion in Fe-doped Cu₂BaSnS₄ (CBTS), namely Cu₂Ba_(1−x)Fe_xSnS₄ (x = 0, 0.1,0.2,0.3) nanoparticles synthesized via a hydrothermal process. The band gap increased from 2.3 to 2.9 eV with respect to doping concentrations due to the energy level hybridization of the valence band minimum. This spectral blue shift is caused by the Moss–Burstein effect originating from the shift of the Fermi level towards higher energies in a heavily doped semiconductor. The particle size is reduced from 121 to 35 nm in Fe-doped CBTS. The electron donor's concentration increased during p to n-type conversion and hence the conductivity in Fe-doped CBTS. The increased charge carrier concentration together with the increased lifetime in Fe-doped CBTS resulted in an increased photo conversion efficiency from 1.86% (Cu₂BaSnS₄) to 2.26% (Cu₂Ba_0.7Fe₀.₃SnS₄).