Low temperatures modification of the p-CuI thin films via a fast trimethylsilyl iodide treatment

This paper reports a facile method to modulate the electrical properties of copper iodide (CuI) thin films, which have attracted considerable attention as a promising transparent conducting p-type semiconductor. Trimethylsilyl iodide (TMSI) was used as an agent for the fast iodination treatment of p-CuI, even at a low processing temperature of 60 °C. A TMSI treatment of less than 30 µL was effective in improving the surface morphology of CuI thin films. The optimal TMSI treatment with 20 µL enhanced the electrical properties of p-CuI by increasing the hole concentration without degrading the optical transmittance. As the TMSI content increased from 0 to 20 µL, the hole concentration of the CuI thin films increased from 4.06 × 10¹⁹ to 8.82 × 10¹⁹ cm⁻³. The TMSI treatment eliminated I-vacancies while forming Cu-vacancies that acted as an acceptor dopant. Therefore, the hole concentration in CuI thin films increased with the TMSI treatment. The performance of p-CuI/n-ZnO diodes, such as on/off ratio, turn-on voltage, and ideality factor, was enhanced by the facile TMSI treatment.