Room-temperature synthesized copper iodide thin film as degenerate p-type transparent conductor with a boosted figure of merit

Significance The lack of high-performance p-type transparent conductors (TCs) has been a main obstacle for the development of transparent electronics. In this study, we overcome this challenge in achieving simultaneously high conductivity and transparency for p-type TCs by developing the degenerate wide-bandgap semiconductor cuprous iodide (CuI). We propose industrially applicable techniques including room-temperature physical deposition by reactive sputtering for thin-film growth and iodine doping of CuI. The obtained CuI polycrystalline thin films exhibit record high conductivity as well as a high transparency, resulting in a 100× improvement of the figure of merit compared with any other p-type transparent conducting material. These results indicate significant advances in the development of p-type TCs toward their practical use.