Metal halide perovskite, APbX3 (A is a cation and X is a halide), nanocrystals are an emerging class of nanomaterials with high photoluminescence quantum yield and easily tunable emission wavelengths. For efficient optoelectronic device applications, these nanocrystals need to be stable, with charge transport-compatible ligands and tunable energy-level alignment. We developed a two-step ligand-exchange strategy, in which the long-carbon-chain ligands on all-inorganic perovskite CsPbX3 nanocrystals are replaced with relatively short halide-ion-pair ligands. We demonstrate ultra-air- and photostable films of CsPbX3 nanocrystals by using an inorganic–organic hybrid ion pair as the capping ligand. This passivation approach to perovskite nanocrystals yields high photoluminescence quantum yield with unprecedented operational stability in ambient conditions and high pump fluences, thus overcoming a major challenge impeding the development of perovskite-based applications. Green and blue light-emitting diodes made from the halide-ion-pair-capped nanocrystals exhibit high external quantum efficiencies compared with the untreated nanocrystals. We also demonstrate the integration of these nanocrystals as color converters for gigabit-rate data transmission with visible light communication systems. Finally, we designed an in situ doping approach for perovskite nanocrystals with heterovalent Bi3+ ions by hot injection to precisely tune their band structure and excited-state dynamics. This synthetic method allowed us to map the impact of doping on charge transfer from the nanocrystals to different molecular acceptors. We demonstrate that charge transfer at the interface of nanocrystals can be tuned and promoted by metal ion doping. We find that doping increases the energy difference between states of the molecular acceptor and the donor moieties, subsequently facilitating the interfacial charge transfer process. Our work paves the way to further the exploitation of perovskite nanocrystal materials in optoelectronics through judicious doping and surface engineering.

Metal halide perovskite nanocrystals: Doping and surface-engineering for efficient optoelectronics

254th National Meeting (2017)

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