Adjustment of optoelectronıc propertıes of ındıum-doped zno thın-fılm photodetectors by sn dopıng

In this thesis, Sn-doped In:ZnO thin films were deposited on glass substrates using the ultrasonic spray pyrolysis technique and investigated for UV photodetector applications. In:ZnO films containing 0, 0.5, 1, and 2 wt.% Sn were prepared to evaluate the influence of Sn doping on the structural, optical, and optoelectronic properties. X-ray diffraction analysis confirmed that all films retained the hexagonal wurtzite structure of ZnO without secondary phase formation, indicating successful incorporation of In and Sn into the ZnO lattice. Increasing Sn content led to a reduction in crystallite size and changes in preferred crystal orientation. Optical measurements showed a sharp absorption edge around 380–400 nm for all samples, while high transparency in the visible region was preserved for low and moderate Sn concentrations. Photoluminescence results revealed strong near-band-edge emission and Sn-dependent defect-related visible emission, indicating that Sn doping modifies the defect structure and recombination processes. Electrical and optoelectronic measurements demonstrated that Sn significantly affects charge transport and UV photoresponse. Higher Sn concentrations reduced the film resistance due to the donor nature of Sn⁴⁺ ions. Under 365 nm UV illumination, all devices exhibited clear photoconductive behavior. The 2% Sn-doped In:ZnO photodetector showed the highest responsivity and external quantum efficiency, while the 1% Sn-doped film exhibited the fastest and most stable photoresponse. These results demonstrate that Sn doping is an effective approach to optimize In:ZnO thin films for UV photodetector applications.