Boosting tunable blue luminescence of halide perovskite nanoplatelets through post-synthetic surface trap repair

TL;DR

This study develops a surface trap repair method for CsPbBr3 nanoplatelets, significantly boosting blue luminescence efficiency, stability, and emission tunability for light-emitting applications.

Contribution

It introduces a post-synthetic surface defect repair technique that enhances blue emission quantum yield and stability in halide perovskite nanoplatelets.

Findings

Photoluminescence quantum yield increased to 73%

Blue emission tunable between 432 and 497 nm

Nanoplatelets exhibit high stability under UV exposure

Abstract

The easily tunable emission of halide perovskite nanocrystals throughout the visible spectrum makes them an extremely promising material for light-emitting applications. Whereas high quantum yields and long-term colloidal stability have already been achieved for nanocrystals emitting in the red and green spectral range, the blue region currently lags behind, with low quantum yields, broad emission profiles and insufficient colloidal stability. In this work, we present a facile synthetic approach for obtaining two-dimensional CsPbBr3 nanoplatelets with monolayer-precise control over their thickness, resulting in sharp photoluminescence and electroluminescence peaks with a tunable emission wavelength between 432 and 497 nm due to quantum confinement. Subsequent addition of a PbBr2-ligand solution repairs surface defects likely stemming from bromide and lead vacancies in a sub-ensemble of weakly emissive nanoplatelets. The overall photoluminescence quantum yield of the blue-emissive colloidal dispersions is consequently enhanced up to a value of 73+-2 %. Transient optical spectroscopy measurements focusing on the excitonic resonances further confirm the proposed repair process. Additionally, the high stability of these nanoplatelets in films and to prolonged UV light exposure is shown.