Drushliak Viktoriia, Szafrański Marek
Faculty of Physics, Adam Mickiewicz University, Uniwersytetu Poznańskiego 2, 61-614Poznań, Poland.
Inorg Chem. 2022 Sep 12;61(36):14389-14396. doi: 10.1021/acs.inorgchem.2c02253. Epub 2022 Sep 1.
CsPbBr belongs to all inorganic perovskite-related quasi-two-dimensional materials that have attracted considerable attention due to their potential for optoelectronic applications. In this study, we solve numerous controversies on the physical properties of this material. We show that optical absorption in the visible spectrum and green photoluminescence are due to microcrystallites of the three-dimensional CsPbBr perovskite settled on the CsPbBr plates and that carefully cleaned crystal plates are devoid of these features. The high-pressure structural and spectroscopic experiments, performed on the single crystals free of CsPbBr impurities, evidenced that the layered tetragonal structure of CsPbBr is stable at least up to 6 GPa. The absorption edge is located in the ultraviolet at around 350 nm and continuously red shifts under pressure. Moderate band gap narrowing is well correlated to the pressure-induced changes in the crystal structure. Although the compressibility of CsPbBr is much higher than for CsPbBr, the response in optical properties is weaker because the Pb-Br layers responsible for the optical absorption are much less affected by hydrostatic pressure than those built of Cs cations. Our study clarifies the confusing data in the literature on the optical properties and thermodynamic stability of CsPbBr.
CsPbBr属于所有无机钙钛矿相关的准二维材料，因其在光电子应用方面的潜力而备受关注。在本研究中，我们解决了关于这种材料物理性质的众多争议。我们表明，可见光谱中的光吸收和绿色光致发光是由于沉积在CsPbBr板上的三维CsPbBr钙钛矿微晶引起的，并且经过仔细清洁的晶体板没有这些特征。对不含CsPbBr杂质的单晶进行的高压结构和光谱实验表明，CsPbBr的层状四方结构至少在6 GPa压力下是稳定的。吸收边缘位于紫外区域，约为350 nm，并且在压力下连续红移。适度的带隙变窄与压力引起的晶体结构变化密切相关。尽管CsPbBr的可压缩性远高于CsPbBr，但光学性质的响应较弱，因为负责光吸收的Pb-Br层受静水压力的影响远小于由Cs阳离子构成的层。我们的研究澄清了文献中关于CsPbBr光学性质和热力学稳定性的混乱数据。
