Ligand Engineering of CsPbI3 Quantum Dots for Efficient Solar Cells

Abstract

Perovskite quantum dots (PQDs) have gained significant attention due to their exceptional optical and electronic properties, rendering them promising materials for various optoelectronic applications, such as single-junction solar cells because of the multiple exciton generation effects. To improve the electrical properties of CsPbI3 PQDs, ligand engineering was explored by introducing short-chain ligands to exchange the original long-chain ligands on the PQD surface during the purification process. However, the short-chain ligands suffer from low solubility in the anti-solvent, resulting in insufficient ligand exchange. To address this issue, we developed an in-situ ligand exchange (ILE) strategy to promote the replacement of long-chain ligands with short-chain ones, leading to improved surface chemistry. In this work, 4-methoxyphenethylammonium iodide (CH3O-PEAI) was demonstrated as the short-chain ligand in the ILE strategy, thereby modifying halide vacancy trap states, and promoting carrier transportation and extraction. As a result, the ILE-CsPbI3-based solar cells achieved a higher power conversion efficiency of 14.4% with a high open circuit voltage (VOC) of 1.23 V and exceptional long-term durability due to higher hydrophobicity.