Light emission from halide perovskite semiconductors: bulk crystals, thin films, and nanocrystals

Halide perovskites are attracting attentions as a novel class of semiconductor materials for devices such as solar cells, light-emitting diodes, lasers, and photodetectors. High-quality perovskite crystals can be fabricated with different forms such as bulk crystals, thin films and nanocrystals. These different geometries influence photoluminescence (PL) properties, and the characteristic differences of PL spectra between bulk single crystals and polycrystalline thin films are originated from the carrier diffusion and PL reabsorption. Nanocrystals exhibit optical properties different from their bulk counterparts due to size effects. Furthermore, the bandgap energies of perovskites can be tuned over a wide range by controlling the constituents. Unique anti-Stokes PL and high-order harmonic generation have also been demonstrated in nanocrystals in addition to bulk crystals and thin films. In this review article, we provide a brief summary of the PL and nonliear light emission properties of perovskite semiconductors. We first discuss the influence of the carrier diffusion and PL reabsorption on the PL spectra and dynamics of thick samples, and then the impact of the electron–phonon interactions on PL spectra in bulk crystals and nanocrystals. The last part of this review is devoted to the light emission phenomena induced by nonlinear optical processes in perovskites.