Effect of the source solution quantity on optical characteristics of ZnO and NiO thin films grown by spray pyrolysis for the design NiO/ZnO photodetectors

Zinc Oxide (ZnO) and Nickel Oxide (NiO) thin films were prepared using the spray pyrolysis technique using three different quantities of solution 5, 10, and 15 ml, to modify their optical properties. Optical characterization of the obtained thin films showed that the bandgap and the transparency of NiO and ZnO decrease with increasing solution quantity. The films are highly transparent making them suitable for optoelectronic applications. It is worth noting that NiO has a low growth rate compared to ZnO due to its larger bandgap. The different parameters obtained for both films are then used to simulate the electrical characteristics and the responsivity of a NiO/ZnO heterojunction based PN photodiode. Both the electrical characteristics and the responsivity improve with increasing quantities of solution. These findings may help to find an optimal design for photodiode fabrication.