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 ∼48 to 86%. The XPS and solid-state ¹H 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 ∼60%.