Achieving a near-unity photoluminescence quantum yield and high stability of CsPbI3 nanoplatelets by hydroiodic acid-assisted ligand treatment†

Abstract

Perovskite nanoplatelets (NPLs) display excellent photoluminescence (PL) properties and unique shape features, including thickness-dependent bandgap luminescence. However, perovskite NPLs, especially those based on iodides, exhibit poor spectral and phase stability. Herein, we propose a facile strategy to achieve a near-unity PL quantum yield (QY) and high stability of CsPbI₃ NPLs by employing hydrogen iodate (HI) for in situ etching-assisted surface modification of the short-chain strongly bound ligand dodecylamine (DDDAm). It is found that HI can etch off the incomplete octahedron [PbI₆]⁴⁻ on the surface of CsPbI₃ NPLs. Simultaneously, the excessive use of I⁻ ions and the introduction of DDDAm ligands effectively passivate the surface defects of NPLs, significantly improving their radiation recombination rate. As a result, the as-prepared CsPbI₃ NPLs exhibit up to 95% PL QY, maintaining PL characteristics even after 87 days of exposure to the atmospheric environment. Conversely, untreated CsPbI₃ NPLs display poor phase stability and transform into non-PL features (δ-CsPbI₃) after 21 days. As a proof of concept, we fabricated perovskite LEDs (PeLEDs) using these treated CsPbI₃ NPLs as luminescent layers for calibration. These PeLEDs showcase bright electroluminescence at 600 nm, with a full width at half maximum of 22 nm and an external quantum efficiency of 2.98%. The effective synthesis strategy using HI-assisted ligand treatment presented here is expected to be extended to the synthesis of other perovskite NPLs, thereby accelerating the integration of perovskite NPLs in optoelectronic technology.