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

Abstract

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.

Keywords

chalcogen doping / CuI / high work function electrode / p-type electrode

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