Pressure Effects on Structure and Optical Properties in Cesium Lead Bromide Perovskite Nanocrystals.

Title Pressure Effects on Structure and Optical Properties in Cesium Lead Bromide Perovskite Nanocrystals.
Authors G. Xiao; Y. Cao; G. Qi; L. Wang; C. Liu; Z. Ma; X. Yang; Y. Sui; W. Zheng; B. Zou
Journal J Am Chem Soc
DOI 10.1021/jacs.7b05260
Abstract

Metal halide perovskites (MHPs) are gaining increasing interest because of their extraordinary performance in optoelectronic devices and solar cells. However, developing an effective strategy for achieving the bandgap engineering of MHPs that will satisfy the practical applications remains a great challenge. In this study, high pressure is introduced to tailor the optical and structural properties of MHP-based cesium lead bromide nanocrystals (CsPbBr3 NCs), which exhibit excellent thermodynamic stability. Both the pressure-dependent steady-state photoluminescence and absorption spectra experience a stark discontinuity at ~1.2 GPa, where an isostructural phase transformation regarding Pbnm space group occurs. The physical origin points to the repulsive force impact due to the overlap between the valence electron charge clouds of neighboring layers. Simultaneous bandgap narrowing and carrier-lifetime prolongation of CsPbBr3 trihalide pe-rovskite NCs were also achieved as expected, which facilitates the broader solar spectrum absorption for photovoltaic applications. Note that the values of phase change interval and bandgap redshift of CsPbBr3 nanowires are between the ones for CsPbBr3 nanocubes and the corresponding bulk counterparts, which results from the unique geometrical mor-phology effect. First-principles calculations unravel that the bandgap engineering is governed by orbital interactions with-in inorganic Pb-Br frame through structural modification. Changes of band structures are attributed to the synergistic effect of pressure-induced modulations of Br-Pb bond length and Pb-Br-Pb bond angle for PbBr6 octahedral framework. Furthermore, the significant distortion of lead-bromide octahedron to accommodate the Jahn-Teller effect at much high-er pressure would eventually lead to a direct to indirect bandgap electronic transition. This study enables high pressure as a robust tool to control the structure and bandgap of CsPbBr3 NCs, and thus providing an insight into the microscopic physiochemical mechanism of those compressed MHP nanosystems.

Citation G. Xiao; Y. Cao; G. Qi; L. Wang; C. Liu; Z. Ma; X. Yang; Y. Sui; W. Zheng; B. Zou.Pressure Effects on Structure and Optical Properties in Cesium Lead Bromide Perovskite Nanocrystals.. J Am Chem Soc. 2017. doi:10.1021/jacs.7b05260

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