Layered Germanium Hybrid Perovskite Bromides: Insights from Experiments and First‐Principles Calculations

作者：Xueqing Chang, Daniela Marongiu, Valerio Sarritzu, Nicola Sestu, Qingqian Wang, Stefano Lai, Alessandro Mattoni, Alessio Filippetti, Francesco Congiu, Alessandra Geddo Lehmann, Francesco Quochi, Michele Saba, Andrea Mura, Giovanni Bongiovanni · 发表于：Advanced Functional Materials · 年份：2019 · DOI：10.1002/adfm.201903528 · 被引用次数：34 · 研究领域：Perovskite Materials and Applications、Solid-state spectroscopy and crystallography、2D Materials and Applications

Abstract Metal halide perovskites are maturing as materials for efficient, yet low cost solar cells and light‐emitting diodes, with improving operational stability and reliability. To date however, most perovskite‐based devices contain Pb, which poses environmental concerns due to its toxicity; lead‐free alternatives are of importance to facilitate the development of perovskite‐based devices. Here, the germanium‐based Ruddledsen–Popper series (CH 3 (CH 2 ) 3 NH 3 ) 2 (CH 3 NH 3 ) n −1 Ge n Br 3 n +1 is investigated, derived from the parent 3D ( n = ∞) CH 3 NH 3 GeBr 3 perovskite. Divalent germanium is a promising, nontoxic alternative to Pb 2+ and the layered, 2D structure appears promising to bolster light emission, long‐term durability, and moisture tolerance. The work, which combines experiments and first principle calculations, highlights that in germanium bromide perovskites the optical bandgap is weakly affected by 2D confinement and the highly stereochemically active 4s 2 lone pair preludes to possible ferroelectricity, a topic still debated in Pb‐containing compounds.