Quasi-Type II Core-Shell Perovskite Nanocrystals for Improved Structural Stability and Optical Gain

In recent years, core-shell lead halide perovskite nanocrystals (PeNCs) and their devices have attracted intensive attention owing to nearly perfect optoelectronic properties. However, the complex photophysical mechanism among them is still unclear. Herein, monodispersed core-shell PeNCs coated with an allinorganic cesium lead bromide (CsPbBr3) shell epitaxially grown on the surface of formamidinium lead bromide (FAPbBr(3)) PeNCs were synthesized. Through power- and temperature-dependent photoluminescence (PL) measurements, it is found that the electronic structure of the core-shell FAPbBr(3)/CsPbBr3 PeNCs has a quasi-type II band alignment. The presence of Cs+ in the shell limits ion migration and helps to stabilize structural and optical properties. On this basis, after being exposed to pulsed nanosecond laser for a period, an amplified spontaneous emission (ASE) can be observed, which is attributed to the effective passivation induced by laser irradiation on defects at the interface. The ASE threshold of the core-shell PeNCs showing high structural and optical stability is 447 nJ/cm(2) under pulsed nanosecond optical pumping. The results that are demonstrated here provide a new idea and perspective for improving the stability of perovskite and can be of practical interest for the utilization of the core-shell PeNCs in optoelectronic devices.

Automated summary

Core-shell lead halide perovskite nanocrystals with a quasi-type II band alignment and Cs+ ions in the shell to limit ion migration and stabilize structural and optical properties. After exposure to pulsed nanosecond laser, amplified spontaneous emission (ASE) is observed, attributed to effective passivation of defects at the interface induced by laser irradiation. These core-shell PeNCs demonstrate high structural and optical stability, with an ASE threshold of 447 nJ/cm(2) under pulsed nanosecond optical pumping.