The presence of 6s2 (5s2) lone-pair electrons on the B-site Pb (Sn) in all-inorganic and hybrid halide ABX3 perovskites distinguishes these materials from the familiar tetrahedral semiconductors traditionally employed in optoelectronics and is key to many of their appealing properties. These electrons are stereochemically active, albeit often in a hidden fashion, resulting in unusual and highly anharmonic lattice dynamics that are linked to many of the special optoelectronic properties displayed by this material class. This article describes the connections between this atypical electronic configuration and the electronic structure and lattice dynamics of these compounds. We illustrate how the lone pair leads to favorable bandwidths and band alignments, mobile holes, large ionic dielectric response, large positive thermal expansion, and even possibly defect-tolerant electronic transport. Taken together, the evidence suggests that other high-performing semiconductors may be found among compounds with lone-pair-bearing cations in high symmetry environments and a high degree of connectivity between atoms.

在全无机和杂化卤化物ABX 3的B位Pb（Sn）上存在6 s 2（5 s 2）孤对电子钙钛矿将这些材料与光电子学中传统使用的熟悉的四面体半导体区分开来，并且是它们许多吸引人的特性的关键。这些电子具有立体化学活性，尽管通常以隐藏的方式存在，从而导致异常且高度非谐的晶格动力学，这些动力学与此类材料显示的许多特殊光电特性有关。本文介绍了这种非典型电子构型与这些化合物的电子结构和晶格动力学之间的联系。我们说明了孤对如何导致良好的带宽和能带对准，可移动的空穴，大的离子介电响应，大的正热膨胀，甚至可能是耐缺陷的电子传输。在一起