Unleashing the True Potential of Halide-Rich Perovskites in Superior Charge Transport Dynamics through Strategic Ligand Engineering

Perovskite nanocrystals (NCs) offer significant potential for photovoltaics, but optimizing surface passivation while ensuring efficient charge transport remains a challenge. This study employs oleylammonium bromide (OAmBr) to modulate ligand density in CsPbBr₃ (CPB) NCs, enhancing charge extraction while mitigating surface traps. By systematically varying OAmBr concentrations, we investigate the impact of bromide-rich surface sites and ligand density on charge extraction efficiency, revealing distinct charge transfer mechanisms for FcA and FcAm. Lower ligand densities improve FcA transport by enhancing surface accessibility, whereas FcAm transfer is governed by both ligand density and bromide-rich surface sites. Notably, CPB12 with optimal ligand density, exhibits superior FcAm charge transfer due to its accessible bromide-rich surface. While surface passivation boosts charge transport to hole acceptors, excessive ligand densities (CPB150) hinder extraction. These findings provide a strategic framework for optimizing ligand engineering to enhance perovskite-based photovoltaics.