Deciphering the Role of Water in Promoting the Optoelectronic Performance of Surface-Engineered Lead Halide Perovskite Nanocrystals

Lead halide perovskites are promising candidates for applicability is limited by their structural instability toward moisture. Although a deliberate addition of water to the precursor solution has recently been shown to improve the crystallinity and optical properties of perovskites, the corresponding thin films still do not exhibit a near-unity quantum yield. Herein, we report that the direct addition of a minute amount of water to post-treated substantially enhances the stability while achieving a 95% photoluminescence quantum yield in a NC thin film. We unveil the mechanism of how moisture assists in the formation of an additional NH4Br component. Alongside, we demonstrate the crucial role of moisture in assisting localized etching of the perovskite crystal, facilitating the partial incorporation of NH4+, which is key for improved performance under ambient conditions. Finally, as a proof-of-concept, the application of post-treated and watertreated perovskites is tested in LEDs, with the latter exhibiting a superior performance, offering opportunities toward commercial application in moisture-stable optoelectronics.

Automated summary

Lead halide perovskites are promising materials, but their applicability is limited by their structural instability toward moisture. A recent study showed that the deliberate addition of water to the precursor solution improves their properties, however, near-unity quantum yield is still not achieved. In this research, we directly added a small amount of water to post-treated perovskites and found that it significantly enhanced their stability and achieved a 95% photoluminescence quantum yield in a thin film. We also uncovered the mechanism of how moisture assists in the formation of an additional component and the role of moisture in localized etching, leading to improved performance.