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.