Two-Dimensional Lead-Free Perovskite (C6H5C2H4NH3)2CsSn2I7 with High Hole Mobility.

Two-dimensional (2D) organic-inorganic perovskites have recently undergone rapid development because of their unique optical properties, layered nature, and better environmental stability. Here, we report on a new type of 2D lead-free perovskite (C6H5C2H4NH3)2CsSn2I7 crystals with millimeter size and high field-effect hole mobility synthesized by a solution method. The excellent crystalline quality and phase purity have been verified by X-ray diffraction and low-temperature photoluminescence studies, while the X-ray photoelectron spectroscopy and energy-dispersive spectrometry measurements reveal the successful incorporation of Cs element into the resultant crystals and the absence of Sn4+ in the as-synthesized crystals. The as-synthesized crystals exhibit a high electrical conductivity and a high hole mobility up to 34 cm2·V-1·s-1 at 77 K. The crystals also show a high photoresponse resulting from the excellent optical properties and high electrical conductivity. Our findings show that the lead-free (C6H5C2H4NH3)2CsSn2I7 crystals with excellent optoelectronic properties would be a promising material for electronic and optoelectronic applications.