Doping of Copper(I) Thiocyanate (CuSCN) with Metal Chlorides for p-Channel Thin-Film Transistors

Copper(I) thiocyanate is one of a few candidates among the transparent inorganic semiconductors that enable the realization of p-type thin-film transistors. However, the average hole mobility and, crucially, the obtainable on current level are usually approximately 0.01 cm 2 V –1 s –1 and 10 –6 to 10 –5 A, respectively. In this work, we explored simple, solution-based doping of CuSCN using metal chlorides (MCl x ): CuCl, CuCl 2, SnCl 2, SnCl 4, and CuCl 2:SnCl 4 co-doping. We found that dopants with the metals in the higher oxidation state (CuCl 2, SnCl 4, and co-doping with CuCl 2 and SnCl 4 ) yielded the largest improvement: increasing the hole mobility by >5 times and achieving an on current of ∼5 × 10 –4 A, which is 1–2 orders of magnitude higher than those of other reports, while still showing the gate-induced field effect. Comprehensive characterizations showed that the MCl x dopants were chemically and structurally compatible with the CuSCN host, resulting in no detectable changes in the crystalline properties and only small variations at the local atomic environment. This study demonstrates a simple doping method for CuSCN, a unique transparent semiconductor that has a wide range of applications in electronic and optoelectronic devices.