Surface pre-optimization of a mixed halide perovskite toward high photoluminescence quantum yield in the blue spectrum range

Abstract

The photoluminescence quantum yields (PLQYs) of all-inorganic halide perovskites in the green and red spectral ranges have approached over 90%, overwhelmingly arousing burgeoning interests for creating a revolution in next-generation high-definition displays. However, obtaining pure blue-emitting perovskites with high PLQYs still remains a challenge. Herein, we designed a novel strategy to pre-optimize CsPbCl₃ quantum dots (QDs) using praseodymium(III) chloride (PrCl₃), and then efficient blue-emitting CsPbBr_xCl_3−x QDs were obtained through halide exchange between the optimized CsPbCl₃ and efficient CsPbBr₃ QDs. Specifically, the PrCl₃ optimization simultaneously and efficiently passivated the surface vacancy defects and appropriately reduced the surface long-chain organic ligands of the CsPbCl₃ QDs, synergistically eliminating the deep trap states, and hence considerably suppressing nonradiative recombination. As a result, the radiative recombination rate was enhanced by more than one order of magnitude from 4.3 to 79 μs⁻¹. Benefiting from this, the blue-emitting CsPbBr_xCl_3−x QDs exhibited an admirable PLQY of up to 89%, which is competitive compared with that of the state-of-the-art red and green-emitting perovskites. This strategy provides a unique understanding regarding the low PLQY of blue-emitting perovskites and an efficient method to boost it, which is especially attractive for constructing efficient blue and white light-emitting diodes.