Solution-processed CuI films towards flexible visible-photodetectors: Role of annealing temperature on Cu/I ratio and photodetective properties

This study reports the physical and electrical properties of solution spin-coated CuI films on the thermally oxidized Si substrates according to different annealing temperatures. The planar and cross-sectional scanning electron microscopy (FE-SEM) analysis confirm the formation of dense CuI films on SiO2 substrates. The decrease in the chemical compositional ratio (Cu/I) of prepared CuI films with the rise of annealing temperature is confirmed by energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) analysis. The annealing temperature-dependent study shows that the CuI films annealed at 175 °C for 30 min have the highest photodetection properties (PDPs) under the illumination of a halogen lamp. The higher percentage of recovery (86%) of photocurrent and the lower drift current is obtained for CuI films annealed at 200 °C for 30 min. The wavelength-dependent (RGB illumination) photodetection properties exhibit that CuI films are highly photosensitive under blue LEDs than green and red LEDs. The highest photosensitivity (264.36 ± 10.12%), photoresponsivity (Rph = (45.64 ± 1.68) mA/W), specific detectivity (Dph = (6.56 ± 1.61)× 109 Jones)), normalized photocurrent to dark current ratio (NPDR=(595971.03 ± 31223.18) W−1)), signal to noise ratio (SNR=3.64 ± 0.50), noise equivalent power (NEP=(3.45 ± 1.41) pWHz−1/2)), and linear dynamic range (LDR = 11.23 ± 0.26) dB) for Vb = 1 V, respectively for CuI films under blue-LEDs. For flexible PDPs, 85% of photodetection properties are achieved for flexible CuI films than PDPs on the rigid substrates. The current study reveals that annealing temperature significantly impacts the chemical compositional ratio and photodetection properties of CuI films.