Interfacial defect healing of In2S3/Sb2(S,Se)3 heterojunction solar cells with a novel wide-bandgap InOCl passivator

Abstract

In₂S₃ has been regarded as a promising nontoxic alternative to CdS as an n-type electron transporting layer (ETL) for environmentally friendly antimony chalcogenide solar cells. However, the high-density of vacancy defects in In₂S₃ cause severe interfacial charge recombination in optoelectronic devices. To tackle this issue, herein we successfully incorporate a novel structurally two-dimensional wide-bandgap InOCl as an interfacial passivator between the In₂S₃ buffer layer and Sb₂(S,Se)₃ absorber through a simple InCl₃ post-treatment strategy, which effectively improves the quality of the In₂S₃/Sb₂(S,Se)₃ heterointerface. Through careful experimental and computational studies, we believe that the wide bandgap InOCl passivator plays an important role in defect healing of In₂S₃ at the heterointerface by increasing the vacancy formation energy and thus reducing the density of defect states. Moreover, this interfacial layer contributes to the formation of a more favorable “spike”-like energy band alignment at the ETL/absorber interface and inhibits the transformation of In₂S₃ into In(OH)₃ in moist air. As a result of significantly suppressed detrimental effects from interfacial recombination via positive defect healing, the In₂S₃/InOCl-based Sb₂(S,Se)₃ solar cell obtains a remarkable power conversion efficiency of 5.20%. To the best of our knowledge, this is the champion efficiency reported for In₂S₃-based antimony chalcogenide solar cells.