Faculty of Physics and Engineering, ITMO University, 197101 St. Petersburg, Russia.
Center for Physical Sciences and Technology, LT-10257 Vilnius, Lithuania.
Phys Chem Chem Phys. 2019 Sep 21;21(35):18930-18938. doi: 10.1039/c9cp03656c. Epub 2019 Aug 27.
All-inorganic lead halide perovskites of various compositions have emerged as a prospective family of materials for light-emitting devices and photonic applications. However, a comprehensive study of their structural and electronic properties is still missing. Moreover, thin film fabrication of these perovskites comprising heterohalide anions by wet chemistry approaches also remains challenging. Here we fabricate high-quality CsPbBrCl perovskite thin films using a wet chemical method accompanied by a chemical vapor anion exchange procedure, which allows rigorously studying their optical and structural properties at different compositions. Namely, we present both the numerical and experimental studies of the electronic properties of all-inorganic mixed-halide perovskites, showing their optical absorption, excitonic photoluminescence and exciton binding energy, phase, chemical composition, and band structure and the band gap evolution with a gradual change in x in CsPbBrCl. The results reveal that as Cl ions substitute for Br ones in the perovskite crystal lattice the room-temperature phase does not change its orthorhombic symmetry, whereas the energy of the direct electronic transition from the valence to conduction band at the Γ-point increases nonlinearly. By using the experimentally derived nonlinear dependence it is easy to accurately predict the band gap for any CsPbBrCl perovskite thin film consisting of grains with sizes beyond the quantum confinement regime.
各种组成的全无机卤化铅钙钛矿已成为用于发光器件和光子应用的有前途的材料家族。然而，它们的结构和电子性质的综合研究仍然缺失。此外，通过湿化学方法制造包含异卤化物阴离子的这些钙钛矿的薄膜仍然具有挑战性。在这里，我们使用湿化学方法并结合化学气相阴离子交换程序来制造高质量的 CsPbBrCl 钙钛矿薄膜，这允许在不同组成下严格研究它们的光学和结构性质。也就是说，我们提出了全无机混合卤化物钙钛矿的电子性质的数值和实验研究，展示了它们的光学吸收、激子光致发光和激子结合能、相、化学成分以及带结构和带隙随 CsPbBrCl 中 x 的逐渐变化的演变。结果表明，随着 Cl 离子在钙钛矿晶格中取代 Br 离子，室温相不会改变其正交对称性，而在Γ点处从价带到导带的直接电子跃迁的能量呈非线性增加。通过使用实验得出的非线性依赖性，很容易准确预测任何由晶粒组成的 CsPbBrCl 钙钛矿薄膜的带隙，这些晶粒的尺寸超出了量子限制范围。
