Doping of Copper(I)\nThiocyanate (CuSCN) with Metal\nChlorides for p‑Channel Thin-Film Transistors

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