This work introduces a dual-function KI treatment that simultaneously enhances Sb2(S,Se)3 absorber quality and CdS heterojunction properties. Iodide diffusion passivates bulk defects while improving crystallization and modifies the ETL’s band alignment. The resulting spike-like interface suppresses recombination, achieving a 10.06% PCE. The unified approach demonstrates how single-step processing can address multiple limitations in antimony chalcogenide photovoltaics.
Abstract
The performance of Sb2(S,Se)3-based photovoltaics is largely limited by intrinsic defects in the absorber layer and suboptimal electronic characteristics at the heterojunction. Extensive efforts have been devoted to improving the quality of the absorber layer and distinctly modifying the electron transport layer (ETL) through targeted doping and surface treatments. Herein, a unified approach is presented that simultaneously addresses both of these challenges and establishes a paradigm shift from conventional sequential optimization strategies. A thin layer of KI is spin-coated between the CdS and Sb2(S,Se)3, whereupon annealing, iodide ions diffuse into the Sb2(S,Se)3 film, promoting grain growth, enhancing crystallization, and elevating the work function. Simultaneously, the KI treatment enhances the conductivity of the CdS, adjusts its energy band positions, and creates a favorable spike-like alignment at the heterojunction, effectively suppressing interfacial carrier recombination. Furthermore, the KI treatment also mitigates detrimental vacancy defects (VS/Se) and reduces antisite defects (SbS/Se) within Sb2(S,Se)3 film. Consequently, the champion device exhibits a remarkable power conversion efficiency (PCE) of 10.06%, a significant improvement over the control device’s PCE of 8.14%. This work presents a holistic approach to optimizing both absorber quality and ETL characteristics, offering a promising pathway to enhance the performance of Sb2(S,Se)3-based solar cells.
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