CsPbI3 perovskite quantum dot (PQD) shows high potential for next-generation photovoltaics due to their tunable surface chemistry, good solution-processability and unique photophysical properties. However, the remained long-chain ligand attached to the PQD surface significantly impedes the charge carrier transport within the PQD solids, thereby predominantly influencing the charge extraction of PQD solar cells (PQDSCs). Herein, a ligand-induced energy level modulation is reported for band engineering of PQD solids to improve the charge extraction of PQDSCs. Detailed theoretical calculations and systemic experimental studies are performed to comprehensively understand the photophysical properties of the PQD solids dominated by the surface ligands of PQDs. The results reveal that 4-nitrobenzenethiol and 4-methoxybenzenethiol molecules with different dipole moments could firmly anchor to the PQD surface thoroughly the thiol group to modulate the energy levels of PQDs, and a gradient band structure within the PQD solid is subsequently realized. Consequently, the band-engineered PQDSC delivers an efficiency of up to 16.44%, which is one of the highest efficiencies of CsPbI3 PQDSCs. This work provides a feasible avenue for the band engineering of PQD solids by tuning the surface chemistry of PQDs for high-performing solar cells or other optoelectronic devices. This article is protected by copyright. All rights reserved.
Keywords: band engineering; charge extraction; perovskite quantum dot; photovoltaic performance; solar cell.
This article is protected by copyright. All rights reserved.