Room-Temperature synthesized copper iodide thin filmas degenerate p-Type transparent conductor with a boosted figure of merit

A degenerate p-Type conduction of cuprous iodide (CuI) thin films is achieved at the iodine-rich growth condition, allowing for the record high room-Temperature conductivity of ∼156 S/cm for asdeposited CuI and ∼283 S/cm for I-doped CuI. At the same time, the films appear clear and exhibit a high transmission of 60-85% in the visible spectral range. The realization of such simultaneously high conductivity and transparency boosts the figure of merit of a p-Type TC: its value jumps from ∼200 to ∼17,000 Mω-1. Polycrystalline CuI thin films were deposited at room temperature by reactive sputtering. Their electrical and optical properties are examined relative to other p-Type transparent conductors. The transport properties of CuI thin films were investigated by temperature-dependent conductivity measurements, which reveal a semiconductor-metal transitio depending on the iodine/argon ratio in the sputtering gas.