Boosting Open-Circuit Voltage of AgBiS<sub>2</sub> Quantum Dot Solar\nCells through Post-treatment Passivation

Silver bismuth disulfide (AgBiS<sub>2</sub>) colloidal quantum\ndots (CQDs) have emerged as attractive absorbers in ecofriendly photovoltaics\ndue to their high absorption coefficient and suitable bandgap. However,\nit is a significant challenge to completely eliminate the numerous\ndefect states on the entire surface of CQDs formed in solid-state\nligand exchange. Here, we propose a simple stepwise passivation approach\nin which AgBiS<sub>2</sub> CQD films are subjected to halide post-treatment\nafter conventional surface passivation with iodide. This approach\ncan compensate for the ligand loss on the surface of AgBiS<sub>2</sub>-CQD under a protic solvent attack. It not only largely reduces the\nsurface trap density but also enhances the dielectric-screening effect,\neffectively promoting charge transport. Through gradual passivation\nwith chloride ions and optimizing the thickness of the light-absorber\nlayer, AgBiS<sub>2</sub>-CQD-based solar cells achieved a power conversion\nefficiency of 10.02% with a high open-circuit voltage of 0.581 V,\nwhich is among the highest reported values for this type of photovoltaic\nto date.