Highly transparent and conductive γ-CuI films grown by simply dipping copper films into iodine solution

In this Letter, we demonstrate a simple and environmentally friendly method to grow large-area p-type conductive CuI films by dipping copper films into ethanol solution of iodine at room temperature. The effects of iodine concentration and film thickness on the morphologies, crystalline phases, optical and electrical properties of CuI films were investigated. All the films are γ-CuI with preferential (111) orientation. At the optimized growth condition, the CuI films exhibit a high transmission which exceeds 73% in the visible spectral range and low resistivity of 0.02 Ω cm. These results pave the way for the growth and further application of large-area CuI films in optoelectronic devices.