Super-Bandgap Electroluminescence from Cesium Lead Bromide

TL;DR

This paper reports a novel method to achieve super-bandgap electroluminescence in CsPbBr3 perovskites, enabling higher-energy emission potentially useful for blue LEDs, by exploiting interface effects and quantum confinement.

Contribution

It introduces an alternative approach to tune and stabilize electroluminescence color in halide perovskites beyond traditional halide mixing methods.

Findings

Achieved electroluminescence 0.7 eV higher than the bandgap.

Identified interface recombination and nanocrystal formation as the cause.

Proposed a new strategy for blue emission in perovskite LEDs.

Abstract

Halide perovskites is a new class of semiconductors with exceptional optoelectronic properties. Among many advantages offered by halide perovskites, the bandgap energy can be tuned in a much broader range than what was possible in conventional semiconductors. This was commonly achieved in previous research by mixing different species of halides into solid solutions. The tuned bandgap using this method, however, often underwent an energy shift under optical or electrical stimuli due to halide segregation. In this work, we discovered an alternative approach to achieve super-bandgap electroluminescence from CsPbBr3. The peak energy of the light emission can be 0.7 eV higher than the reported bandgap energy. Evidence pointed to the radiative recombination at the perovskite-PEDOT:PSS interface being responsible for the unexpected blueshift of electroluminescence. We speculated that perovskite nanocrystals were formed therein and produced higher-energy photons due to quantum confinement. The results suggested an alternative strategy to manipulate and stabilize the color of electroluminescence and achieve particularly blue emission in perovskite-based LEDs.