Room Temperature Wafer‐Scale Synthesis of Highly Transparent and Conductive p‐Type Sulfur‐Doped Copper Iodide

The development of high‐performance p‐type transparent conductors (TCs) is essential for advancing transparent and flexible electronics yet remains a significant challenge due to the lack of effective p‐type materials with high hole mobility and sufficiently large work function. Copper iodide (CuI) has emerged as a promising p‐type TC due to its wide bandgap (~3.1 eV), high transparency (>70%), and excellent hole transport properties. However, optimizing its electrical and optical performance requires precise control over its crystallinity and carrier concentration. Here, we present a room temperature, wafer‐scale gas‐phase synthesis method for sulfur‐doped CuI, where sulfur pre‐doping significantly enhances crystal quality and carrier mobility while achieving excellent visible‐light transmittance (86%), ultra‐low sheet resistance (75 Ω sq −1 ), and a high work function (>5.9 eV), resulting in a record‐high figure of merit (95 000 (MΩ) −1 ) among p‐type TCs. Our pre‐doping strategy yields superior electrical and optical properties without compromising material stability. Furthermore, this scalable and damage‐free synthesis method offers a practical pathway for integrating CuI into next‐generation transparent electronics, optoelectronics, and flexible devices.