Luminescence Properties and Mechanisms of CuI Thin Films Fabricated by Vapor Iodization of Copper Films

Copper iodide (CuI) thin films were grown on Si(100) substrates using a copper film iodination reaction method. It was found that gamma-CuI films have a uniform and dense microstructure with (111)-orientation. Transmission spectra indicated that CuI thin films have an average transmittance of about 60% in the visible range and the optical band gap is 3.01 eV. By checking the effect of the thickness of the Cu films and annealing condition on the photoluminescence (PL) character of CuI films, the luminescence mechanisms of CuI have been comprehensively analyzed, and the origin of different PL emissions are proposed with Cu vacancy and iodine vacancy as defect levels.