Fabrication of cost-effective lead-free silver bismuth iodide based mesoscopic Rudorffite solar cells

Lead-free Ag–Bi–I Rudorffite materials, specifically AgBiI₄, Ag₂BiI₅, Ag₃BiI₆ and AgBi₂I₇, have garnered substantial attention as prospective alternatives to lead halide perovskites in solar cell technology. Rudorffite-based solar cells have conventionally employed a mesoporous structure, integrating unstable and costly hole-transport layers (HTLs) in conjunction with noble metal electrodes. This study presents carbon-based, all-inorganic AgBiI₄, Ag₂BiI₅, Ag₃BiI₆ and AgBi₂I₇ Rudorffite solar cells that circumvent the need for HTLs and noble metal electrodes. The absorber layers composed of AgBiI₄, Ag₂BiI₅, Ag₃BiI₆ and AgBi₂I₇ materials were synthesized via melt-solidification. Notably, Ag₂BiI₅ based solar cell achieved PCE of 0.93 % among all the Silver Bismuth Iodide (SBI) devices which is the highest efficiency reported for Ag₂BiI₅ solar cell to date. The corresponding solar cell parameters include an open-circuit voltage (V_oc) of 0.634 V and a short-circuit current (J_sc) of 3.63 mA/cm². Consequently, our work presents a pathway toward developing Rudorffite solar cells with simplified fabrication methods and reduced cost.