Defect energy level and transition mechanism of CuI thin film by low-temperature spectrum

Copper Iodide (CuI) thin films were prepared by iodination technique. The transmission spectrum showed band gap of prepared CuI thin film was 3.0 eV. A main emission at 404 nm (near-band emission), a defect emission at 412 nm (CBM -> V-Cu) and another defect emission at 710 nm (V-I -> Cu-I) were found in photoluminescence spectrum. Transition mechanism of CuI was proposed by low-temperature photoluminescence spectrum. Emission at 412 nm is greatly affected by ambient temperature. The results show that the thermal activation at room temperature inhibits the emission at 412 nm, and the inhibition decreases when the temperature dropped, resulting in an increase in emission intensity at 412 nm and a decrease in emission intensity at 710 nm.