Carrier cooling dynamics in inorganic perovskites

Inorganic perovskites represent a very promising alternative to hybrid organic-inorganic perovskites, given their better long-term stability and impressive radiative yield. In fact, such materials are extremely attracting not... [ view full abstract ]

Inorganic perovskites represent a very promising alternative to hybrid organic-inorganic perovskites, given their better long-term stability and impressive radiative yield. In fact, such materials are extremely attracting not only for tandem photovoltaic cells but also for manufacturing efficient LEDs and lasers, allowing to cover a spectral range from NUV to NIR depending on the material composition. Despite the huge activity in this hot research field, quite incomplete and fragmentary is the knowledge on fundamental physics aspects, in particular concerning the relaxation rates of carriers and excitons. In this contribution, we present a detailed experimental investigation of the photoluminescence (PL) dynamics at the picosecond and nanosecond time-scale of carriers and excitons in CsPbBr₃ thin films and microstructures, deposited on different substrates (glass and metals), and also single crystals.
Non-resonant and resonant excitation are used to bring evidence of the different thermalization conditions and provide quantitative information of the characteristic time-scale of the thermalization process. Time-resolved PL spectra, varying several parameters (temperature, excitation density and wavelength) are discussed (see as example Fig.1). Our results show the occurrence of a very slow cooling process, which manifests itself even at very low excitation density, and then cannot be ascribed to Auger recombination or to screening of the electron-phonon interaction. The experimental data give evidence that recombination heating plays a fundamental role in the slowing down of the carrier thermalization.