Photoluminescence Loss and Recovery of α-CsPbI3 Quantum Dots Originated from Chemical Equilibrium Shift of Oleylammonium

α-CsPbI3 perovskite quantum dots (PQDs) have great potentials in red-emitting LED and solar cell applications. However, their instability with quick photoluminescence loss with time greatly limits their development. In this study, we found that the nonluminous aged α-CsPbI3 PQDs instantly regained fluorescence emission after a surface treatment with trioctylphosphine. Meanwhile, this surface treatment also worked on fresh α-CsPbI3 PQDs to enhance photoluminescence emission. The structures and compositions of fresh and aged PQDs before and after surface treatment were analyzed in detail. We demonstrated that a surface chemical equilibrium shift mechanism involving oleylammonium led to the PL loss and recovery of α-CsPbI3 PQDs. This chemical equilibrium shift also played an important role in other PQD stabilities against long term storage, temperature, UV irradiation and ethanol, which were all significantly improved after treatment. The treated α-CsPbI3 PQDs were phase stable for more than 6 months. Oleic ...