Hydrophobic stabilizer-anchored fully inorganic perovskite quantum dots enhance moisture resistance and photovoltaic performance

Advances in surface chemistry and manipulation of fully inorganic CsPbI₃ perovskite quantum dots (CsPbI₃-QDs) have enabled improving the charge transport and photovoltaic performance of CsPbI₃-QD thin films by replacing their native long-chain, insulating ligands with short-chain ligands. However, the conventional approach based on formamidinium (FA) replacement removes the hydrophobic protective layer, opening the path for moisture penetration and resulting in poor device stability. We demonstrate that short-chain and hydrophobic phenethylammonium (PEA) cations, instead of FA, are efficiently incorporated only onto CsPbI₃-QD surfaces, confirmed by Fourier-transform infrared, H nuclear magnetic resonance and density functional theory calculations. PEA incorporation leads simultaneously to improved photovoltaic performance and moisture stability of resultant CsPbI₃-QDs without any change in size, fully inorganic composition, and dimensionality of CsPbI₃-QDs. Therefore, PEA-incorporated CsPbI₃-QD solar cells show a high device power conversion efficiency of 14.1% and high moisture stability, retaining over 90% of the initial performance after 15 days under ambient conditions.