Wide‐Range‐Tunable p‐Type Conductivity of Transparent CuI1−xBrx Alloy

Abstract Transparent p‐type semiconductors with wide‐range tunability of the hole density are rare. Developing such materials is a challenge in the field of transparent electronics that utilize invisible electric circuits. In this paper, a CuI–CuBr alloy (CuI 1− x Br x ) is proposed as a hole‐density‐tunable p‐type transparent semiconductor that can be fabricated at room temperature. First‐principles calculations predict that the acceptor state originating from copper vacancies in CuBr is deeper than that in CuI, leading to the hypothesis that the hole density in CuI 1− x Br x can be tuned over a wide range by varying x between 0 and 1. The experimental results support this hypothesis. The hole density in CuI 1− x Br x polycrystalline alloy layers can be tuned by over three orders of magnitude (10 17 –10 20 cm −3 ) by varying x . In other words, the p‐type conductivity of the CuI 1− x Br x alloy shows metallic and semiconducting properties. Such alloy layers can be prepared at room temperature without sacrificing transparency. Furthermore, CuI 1− x Br x forms transparent p–n diodes with n‐type amorphous In–Ga–Zn–O layers, and these diodes have satisfactory rectification performance. Therefore, CuI 1− x Br x alloy is an excellent p‐type transparent semiconductor for which the p‐type conductivity can be tailored in a wide range.