Enriched optoelectronic properties of cobalt-doped ZnO thin films for photodetector applications

Cobalt-doped ZnO (ZnO:Co) thin films were synthesized using the chemical bath deposition technique for their potential application in ultraviolet (UV) photosensing. All the prepared samples were characterized using XRD, FESEM, EDX, PL, XPS, and UV–Vis absorption techniques. The UV photosensing property of the thin films was examined under the illumination of UV light (365 nm). The structural and morphological investigations reveal that the ZnO:Co samples have a hexagonal wurtzite crystal structure with nanowire morphology. An increase in crystallite size and a decrease in the bandgap of the samples were observed owing to the replacement of the Co2+ ions in the regular sites of Zn2+. The PL spectra show some defect emission peaks in the visible region because of the occurrence of oxygen vacancies, which suggests a high photoabsorption property of the samples. The XPS study was performed to understand the existence of elements and their binding states in the fabricated thin films. The UV photosensing studies reveal that the highest responsivity of 0.918 AW−1 was achieved for the ZnO:Co (1%) sample.