Photon recycling in perovskite materials involves the repeated absorption and re-emission of photons within the material, significantly enhancing light emission efficiency and stability. This process is particularly impactful in cesium lead halide perovskites (e.g., CsPbBr₃), where high radiative efficiency and waveguide effects enable long-distance photon propagation and spectral redistribution. Our work investigates these mechanisms in single-crystal CsPbBr₃ microwires, demonstrating their potential for lasers, light-emitting diodes (LEDs), and photodetectors.
We have found that photon recycling in CsPbBr₃ Microwires has spectral redistribution in which Photoluminescence (PL) spectra shift from 525 nm to 545 nm as photons propagate over 100 μm along microwires, revealing iterative self-absorption and re-emission. There were also delayed PL kinetics as rise times in PL dynamics scale with propagation distance, confirming photon recycling rather than carrier diffusion (diffusion length ~0.1 μm). And quantitative modeling shows near-unity internal radiative efficiency, critical for light-emitting applications, demonstrating there is high radiative efficiency (ACS Energy Lett. 2018, 3, 1492–1498; ACS Materials Lett. 2023, 5, 1411–1419)
(a) Linear absorption spectrum of an individual microwire. Inset: Left part, schematics of linear absorption measurements using white light; right part, variable length excitation–collection measurements using the same pair of objectives, with the bottom one translated along the microwire. (b) PL spectra as a function of separation s. Spectra are normalized at the maximum emission intensity. Excitation power 20 μW. Inset: PL emission intensity at the 530 nm peak as a function of separation distance s.
Photon recycling in CsPbBr₃ microwires enhances emission efficiency and spectral control, analogous to advancements in perovskite-quantum shell hybrids (e.g., 2.3× EQE improvement in LEDs). Embedding nanocrystals (e.g., 0D Cs₄PbBr₆) further boosts PL quantum yield and stability, aligning with trends in composite perovskite films. Harnessing photon recycling and waveguiding in perovskite microstructures offers a pathway to high-performance optoelectronic devices, combining efficiency, stability, and spectral tunability.