Effect of reabsorption and photon recycling on photoluminescence spectra and transients in lead-halide perovskite crystals

Explaining the time-dependent evolution of photoluminescence spectra of halide perovskite single crystals after pulsed excitation requires the consideration of a range of physical mechanisms, including electronic transport, recombination and reabsorption. The latter process of reabsorption and re-generation of electron-hole pairs from a photon created by radiative recombination in the single crystal itself is termed photon recycling and has been a highly controversial topic. We use photoluminescence experiments performed under different illumination conditions combined with numerical simulations that consider photon recycling to show which parameters affect temporal decays, spectral shifts and differences in the illumination direction. In addition, we use numerical simulations with and without photon recycling to understand the relative importance of charge-carrier transport and photon recycling. We conclude that under most relevant illumination conditions and times after the pulse, electronic transport is more important than photon recycling for the spectral behavior of the transients. However, inclusion of photon recycling is imperative for the understanding of the absolute density of electrons and holes present in the crystal during a certain time after the pulse.