p-type CuI films with optimized optoelectronic performance were synthesized by solid-phase iodination of Cu3N precursor films at room temperature. The effect of the deposition power of Cu3N precursors on the structural, electrical, and optical properties of the CuI films was systematically investigated. X-ray diffraction (XRD) results show that all the CuI films possess a zinc-blende structure. When the deposition power of Cu3N precursors was 140 W, the CuI film presents a high transmittance above 84% in the visible region, due to its smaller root-mean-square (RMS) roughness values of 9.23 nm. Moreover, these films also have a low resistivity of 1.63 ×10-2 Ω·cm and a boosted figure of merit (FOM) of 140.7 MΩ-1. These results are significant achievements among various p-types TCOs, confirming the promising prospects of CuI as a p-type transparent semiconductor applied in transparent electronics.