High photoactive black phase stability of CsPbI3 nanocrystals under damp-heat conditions of 85 °C and 85% relative humidity

CsPbI3 as a newly emerging semiconductor material has displayed tremendous prospects for optoelectronic applications. However, the poor photoactive black-phase stability limits its further application. In this work, we introduce transition metal nickel ion (Ni2+) as a B-site substitute into CsPbI3 nanocrystals (NCs) to stabilize their black phase. The optimized CsPbI3 NCs film presents a record photoactive black-phase stability time of 54 hours under the conditions of 85 degrees C and 85% relative humidity, over 108 times that of the undoped film. Furthermore, the Ni2+-doped CsPbI3 NCs solutions maintain bright red emission after vigorous stirring with an equal volume of water for 200 hours (the undoped solution is almost completely quenched), and also show bright red emission after being stored in the air for 200 days (the undoped solution is completely quenched within 43 days). Meanwhile, the photoluminescence quantum yield increased from 31.48% for undoped CsPbI3 NCs to 87.69% for doped Ni-3.65% CsPbI3 NCs. We suggest that these outstanding stabilities and excellent optical properties can mainly be attributed to the increased defect formation energy after rational Ni doping and lattice adjustment by partial replacement of Pb2+ with small-sized Ni2+. Our work provides guidance for the synthesis of phase-stabilized CsPbI3 NCs and an insight into the effect of B-site doping in a perovskite lattice, providing a promising pathway to construct stable and efficient photoelectronic devices.

Automated summary

In this work, transition metal nickel ion (Ni2+) was introduced into CsPbI3 nanocrystals (NCs) to stabilize their black phase. The optimized CsPbI3 NCs film exhibited a record photoactive black-phase stability time of 54 hours. The doped Ni2+-CsPbI3 NCs solutions maintained bright red emission even after vigorous stirring and long-term storage, showing improved stability and photoluminescence quantum yield.