Solution-Processed Copper Iodide Film as a p-Type Electrical Conductor and Their Applications

Solution-processed inorganic electrical conductors are low-cost and stable to the environment compared to the organic or various nanowire materials. Developing such materials is a challenge in the field of electronics, sensors, and displays that contain transparent electrodes and carrier injectors. Here, we report on copper iodide (CuI) thin films as a high carrier density p-type electrical conductor. The CuI films can be fabricated by a simple solution process at low temperature (∼100 °C) annealing, and they exhibited a high hole carrier density (9.8 × 1018 cm–3) with a sheet resistance of 2.2 kohm sq–1, resulting in the p-type conductivity. In addition, owing to its wide band gap nature, the films appear clear and showed a high transmittance of >80% in the visible region. Based on these electrical/optical properties, we employed the CuI films as a source-drain electrode and sensing material into thin-film transistors and strain sensors, respectively. Both devices have satisfactory switching and sensing performance. This work suggests that the CuI material can be a promising candidate for p-type electrical conductors for various electronics and sensor applications.