Enhanced transmittance and mobility of p-type copper iodide thin films prepared at room temperature via a layer-by-layer approach

High-quality, transparent, conducting, p-type gamma-CuI thin films are prepared via an innovative layer-by-layer procedure based on the traditional simple iodination of Cu films (referred to as the LBL-I method) at room temperature (RT). The structure, morphology, and optoelectronic properties of the gamma-CuI are investigated as functions of the per layer thickness. The final thicknesses of LBL-I gamma-CuI films are consistent with that in the film prepared by the traditional one-step method (TOS). X-ray diffraction analysis reveals that all the films are polycrystalline with the most dominant (111) direction of the zinc blende structure, indicating the facile and successful fabrication of gamma-CuI. Compared with the TOS film, the LBL-I films display enhanced transmittance and mobility. The higher transmittance of > 80% in the visible region of LBL-I films was attained due to the smaller root-mean-square roughness values of 23-28 nm. The 50 nm/l LBL-I CuI films have mobility values of 6.9-9.4 cm(2) V-1 s(-1), and lower resistivity of 0.039-0.05 Omega cm, which assist studies on applications of gamma-CuI thin films in transparent electronics.