Se-driven charge transport in AgBiS ₂ for photovoltaic application

Engineering notes

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Chinese explanation / 中文解读

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Original abstract

Abstract AgBiS 2 has emerged as a promising photovoltaic absorber, with power conversion efficiencies rapidly increasing and recently surpassed the 10% milestone. In this work, AgBiS 2 thin films are fabricated by coating a Ag-Bi-S molecular precursor ink onto glass substrates, followed by post-sulfurization and post-selenization treatments. The influence of chalcogen chemistry and processing temperature on the structural, morphological, optical, and electrical properties of AgBiS 2 /AgBiSe 2 films is systematically investigated. Sulfurization yields crystalline cubic AgBiS 2 films, although with large electrical resistivity. Structural and compositional analyses indicate that defect-induced carrier compensation, potentially originating from silver vacancies and the coexistence of Bi 2 S 3 secondary phases, is responsible for the suppressed electrical conductivity. To overcome this limitation, selenization is explored as a post-treatment strategy. The selenized films crystallize into the hexagonal AgBiSe 2 phase and exhibit improved electrical conductivity, with charge carrier densities on the order of 10 14 cm -3 . UV-Vis-NIR spectroscopy reveals indirect band gaps in the range of 0.65–0.78 eV for selenized films, which are lower than those of the sulfurized counterparts (0.89–0.97 eV). Such band gap narrowing enables enhanced utilization of the infrared region of the solar spectrum, making AgBiSe 2 attractive as a bottom absorber in multijunction or tandem solar cells. As a proof-of-concept, a solar cell fabricated using sulfurized AgBiS 2 demonstrates the feasibility of device integration. Overall, this study establishes selenization as an effective route to modulate the optoelectronic properties of AgBiS 2 -based absorbers and provides insights into defect chemistry and chalcogen substitution in silver bismuth chalcogenides.

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