Performance Enhanced Light-Emitting Diodes Fabricated from Nanocrystalline CsPbBr3 with In Situ Zn2+ Addition

Inorganic cesium lead halide perovskite nanocrystals are promising materials for optoelectronic applications as they exhibit high thermal stability alongside precise color tunability and high color purity; however, their optical properties are degraded by surface defects. This work demonstrates a room temperature synthesis of CsPbBr3 nanocrystals facilitating in situ surface passivation via the incorporation of Zn2+ cations. The facile incorporation ZnBr2+ into the precursor solution facilitates Zn2+ and Br- substitution into the nanocrystal surface/subsurface layers to induce passivation of existing Pb2+ and Br- vacancies and increase the photoluminescence quantum yield from similar to 48 to 86%. The XPS and solid-state H-1 MAS NMR techniques show that the key modification is a reduction of the octylamine:oleic acid ratio leading to a near-neutral surface charge; this is accompanied by the appearance of larger nanosheets and nanowires observed by quantitative powder XRD and HR-TEM. The suitability of these perovskite nanocrystals for electrically driven applications was confirmed by the fabrication of light-emitting diodes, which demonstrate that the in situ Zn2+ passivation strategy enhanced the external quantum efficiency by similar to 60%.