Fabrication of homogenous Sb2(S,Se)3 solar cells by close space sublimation using a single alloyed powder source

Abstract

Sulfoselenide Sb2(S,Se)3, as a potential light-harvester, possesses a flexibly tunable bandgap of 1.1–1.7 eV to match solar radiation spectrum. However, the preparation of a homogenous Sb2(S,Se)3 film is still challenging due to the different growth kinetics in sulfide and selenide compound, which consequentially leads to phase separation, lattice disorder and unfavored band level. This dilemma also occurs in the simple and well-established close space sublimation (CSS) method, and poses a devastating carrier recombination in Sb2(S,Se)3 solar cells. Herein, alloyed powders of Sb2(S,Se)3 are exquisitely synthesized by a thorough gas-solid reaction, delivering a uniform and single phase composition distribution as well as finely-tunable S/Se ratio. Compared with a physically mixed powder source (Sb2S3/Sb2Se3), this alloyed Sb2(S,Se)3 source allows for the fabrication of a homogeneous Sb2(S,Se)3 thin film by CSS, rendering improved (hk1) orientation, dense morphology, a more consistent longitudinal S/Se ratio, and enhanced energy level arrangement. These advancements contribute to enhance carrier transport and reduce carrier recombination. As a result, the efficiency of the solar cell is remarkably boosted from 2.59% to 5.46%, which is among of the highest PCE of full-inorganic Sb2(S,Se)3 devices fabricated through the CSS method.