p-type CuI films grown by iodination of copper and their application as hole transporting layers for inverted perovskite solar cells

Abstract

γ-phase copper iodide (γ-CuI) is a wide bandgap p-type semiconductor with a band gap of 3.1 eV, which is suitable for optoelectronic devices like light-emitting diodes and solar cells. A simple and convenient method of iodination of copper film to prepare CuI film was reported. The effects of iodination time, reaction temperature, and copper/iodine ratio on the transparent and conductive properties of CuI film were explored. CuI films with high transmittance over 75% in the visible range and low resistivity of 4.4×10-2 Ω·cm were grown under the optimized iodination time (30 min) and iodination temperature (120℃). The CuI films were adopted as hole transporting layers for CuI/CH3NH3PbI3/PCBM inverted planar perovskite solar cell and a maximum photovoltaic efficiency of 8.35% was obtained. The influences of the transparent and conductive properties of CuI films on the solar cell photovoltaic efficiency were also discussed.