(C<sub>5</sub>N<sub>2</sub>H<sub>14</sub>)GeBr<sub>4</sub>: A 2D Organic Germanium Bromide Perovskite with Strong Orange Photoluminescence Properties
Nan He, Pifu Gong, Xingyu Zhang, Youquan Liu, Linfeng Dong, Zheshuai Lin
Abstract
Hybrid organic–inorganic metal halide (OIMH) perovskites are regarded as potential photoluminescent (PL) materials and have attracted intensive attention. Here, we select 1-methylpiperazine as an organic component and successfully obtain a two-dimensional (2D) Ge-based OIMH perovskite, (1-mpz)GeBr 4 . It features a 2D layered structure composed of distorted [GeBr 6 ] 4– octahedra with organic (C 5 H 14 N 2 ) 2+ located between the layers. (1-mpz)GeBr 4 exhibits strong orange color under ultraviolet (UV) light and possesses good PL stability for over 2 months. The photoluminescence quantum efficiency is measured to be 7.15% at room temperature, which is the largest among all reported low-dimensional Ge-based perovskites. Experimental measurements, combined with first-principles calculations, reveal that its PL property is attributed to self-trapped excitons (STEs) from [GeBr 6 ] 4– groups. From the deduced structure–property relationship, Ge-based OIMH PL perovskites with good stability and high PL efficiency can be expected.