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

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.
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