Grain Engineering for Improved Charge Carrier Transport in Two-Dimensional Lead-Free Perovskite Field-Effect Transistors.

Controlling crystal growth and reducing the number of grain boundaries are crucial to maximize the charge carrier transport in organic-inorganic perovskite field-effect transistors (FETs). Herein, the crystallization and growth kinetics of a Sn(ii)-based 2D perovskite, using 2-thiopheneethylammonium (TEA) as the organic cation spacer, were effectively regulated by the hot-casting method. With increasing crystalline grain size, the local charge carrier mobility is found to increase moderately from 13 cm(2) V-1 s(-1) to 16 cm(2) V-1 s(-1), as inferred from terahertz (THz) spectroscopy. In contrast, the FET operation parameters, including mobility, threshold voltage, hysteresis, and subthreshold swing, improve substantially with larger grain size. The optimized 2D (TEA)(2)SnI4 transistor exhibits hole mobility of up to 0.34 cm(2) V-1 s(-1) at 295 K and a higher value of 1.8 cm(2) V-1 s(-1) at 100 K. Our work provides an important insight into the grain engineering of 2D perovskites for high-performance FETs.