Pressure Effects on Optoelectronic Properties of CsPbBr3 Nanocrystals

The pressure-dependent optoelectronic properties of all-inorganic perovskite CsPbBr3 nanocrystals (NCs) are investigated with steady-state and transient spectroscopy. The steady-state absorption and photoluminescence (PL) spectra under pressure show that CsPbBr3 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 PbBr6 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 CsPbBr3 NCs compression. These results in this work help us to design and optimize the perovskite-based optoelectronic devices of high performance.