Incorporating Guanidinium as Perovskitizer‐Cation of Two‐Dimensional Metal Halide for Crystal‐Array Photodetectors

Abstract Two‐dimensional (2D) hybrid perovskites are recently emerging as a potential family of semiconductors for versatile optoelectronic applications. Currently, the “perovskitizer” moieties are rigidly limited to small‐size cations, while few 2D metal‐halides containing guanidinium cations inside perovskite cages have been studied for photodetection. Herein, we present a new 2D hybrid perovskite, ( i ‐BA) 2 (G)Pb 2 I 7 (where G is guanidinium and i ‐BA is isobutylammonium), which adopts a bilayered framework of {GPb 2 I 7 }. Single‐crystal structure analyses disclose that G cations act as the perovskitizer, confined in the flexible perovskite cages formed by the distorted PbI 6 octahedra. Such inorganic sheets are crucial to the superior semiconducting properties and optical bandgap, as verified by the density functional theory calculation. Furthermore, its planar crystal‐array photodetector shows fascinating photoelectric performance, including a quite low dark current (∼4.6×10 −11 A), a large current switching ratio (∼1.0×10 3 ), and a notable photo‐responsivity of ∼0.72 A W −1 , suggesting great potential of ( i ‐BA) 2 (G)Pb 2 I 7 for photodetection.