Pressure Effects on Optoelectronic Properties of CsPbBr₃ Nanocrystals

The pressure-dependent optoelectronic properties of all-inorganic perovskite CsPbBr 3 nanocrystals (NCs) are investigated with steady-state and transient spectroscopy. The steady-state absorption and photoluminescence (PL) spectra under pressure show that CsPbBr 3 NCs pass through three electronic states (ES-I, ES-II, and ES-III) separated with two knee points located at 0.38 and 1.08 GPa, respectively, which are also confirmed by the PL dynamics. Analyzed with the two-carrier model of free carriers and trapped carriers, the PL dynamics show that the lifetime increases in ES-I, decreases in ES-II, and increases in ES-III for free carriers, while it is almost invariable for trapped carriers. The transformation from ES-I to ES-II is assigned to the contraction of the Pb–Br bond length while the transformation from ES-II to ES-III originated mostly from the distortion of the PbBr 6 octahedron. Apparently, the contraction of the Pb–Br bond and the distortion of octahedra benefit the tailoring of the generation and diffusion of carriers during the CsPbBr 3 NCs compression. These results in this work help us to design and optimize the perovskite-based optoelectronic devices of high performance.