Tunable Ultraviolet Photoresponse in Solution-Processed p–n Junction Photodiodes Based on Transition-Metal Oxides

Solution-processed p–n heterojunction photodiodes have been fabricated based on transition-metal oxides in which NiO and ternary Zn1–xMgxO (x = 0–0.1) have been employed as p-type and n-type semiconductors, respectively. Composition-related structural, electrical, and optical properties are also investigated for all the films. It has been observed that the bandgap of Zn1–xMgxO films can be tuned between 3.24 and 3.49 eV by increasing Mg content. The fabricated highly visible-blind p–n junction photodiodes show an excellent rectification ratio along with good photoresponse and quantum efficiency under ultraviolet (UV) illumination. With an applied reverse bias of 1 V and depending on the value of x, the maximum responsivity of the devices varies between 0.22 and 0.4 A/W and the detectivity varies between 0.17 × 1012 and 2.2 × 1012 cm (Hz)1/2/W. The photodetectors show an excellent UV-to-visible rejection ratio. Compositional nonuniformity has been observed locally in the alloyed films with x = 0.1, which i...