Interfacial defect healing of In2S3/Sb-2(S,Se)(3) heterojunction solar cells with a novel wide-bandgap InOCl passivator

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 Sb-2(S,Se)(3) absorber through a simple InCl3 post-treatment strategy, which effectively improves the quality of the In2S3/Sb-2(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 Sb-2(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.