Enhanced thermal stability of exciton recombination in CsPbI3 perovskite nanocrystals via zinc alloying

Abstract

In this work, the Pb2+ substitution with Zn2+ in CsPbI3 perovskite nanocrystals (PNCs) is partially achieved to improve the optoelectronic properties through temperature-pressure assisted crystallization approach. The spectral and dynamic exciton recombination for zinc alloyed CsPbI3 PNCs are probed with steady-state/time-resolved PL (TRPL), transient absorption (TA) techniques. Compared with pure CsPbI3 PNCs, PLQY can be boosted to 60% when incorporating the optimal amount of ZnI2 in the synthesis, and long-term thermal stability are obtained in a series of red-emitting alloyed CsPbI3 PNCs. Simultaneously, the change of exciton binding energy and average optical phonon energy indicate that weaker nonradiative transition for exciton recombination of zinc alloyed CsPbI3 PNCs than those of CsPbI3 PNCs. TRPL and TA spectroscopy are used to understand the photoinduced carrier relaxation processes. The carrier dynamics reveal that the coupling between Zn-induced lowest excited state and exciton trapping state is promoted in zinc alloyed CsPbI3 PNCs, which can significantly enhance the efficiency of excitonic recombination. The improved performance of PLQY and thermal stability makes these zinc alloyed CsPbI3 PNCs as appropriate perovskite materials for efficient optoelectronic devices.