Effects of incorporating manganese in CdS thin films elaborated by CBD and the performance of Schottky diodes TCO/CdS:Mn/C

Abstract

This study focuses on manganese doped CdS thin films by chemical bath deposition (CBD). Thin films and Schottky diodes of CdS and CdS:Mn are synthesized by a simple chemical route. The influence of the incorporation of Mn2+ cations in the crystalline structure of CdS has been characterized by techniques such as XRD, SEM, XPS, UV–Vis spectroscopy, and I–V curves. Doped thin films have a uniform hexagonal structure and preferentially grow along the (100) and (002) planes. The higher the amount of Mn2+ cations, the preferential orientation of the (100) plane gradually disappears, while the undoped sample shows a preferential orientation in the (002) plane. In addition, the morphology, when incorporating manganese, exhibits a drastic change, generating scale-like and needle-like structures, and the average size of the particles varies from 67 nm to 107 nm, in contrast to virgin CdS particles that show a mean size of 23 nm and spherical structures. The variation of the bandgap is 0.067 eV due to the presence of the preferential orientation in the (100) crystal plane in the Mn-doped samples and the doping increase in crystallite size. Doped Schottky diodes exhibit a saturation current of 2 nA and a potential barrier of 0.66 eV, compared to undoped diodes that exhibit a saturation current of 0.93 nA and a potential barrier of 0.823 eV. In addition, it was possible to modify the rectification speed of the diodes by almost 70 % by incorporating manganese. Overall, our study reveals that there is great potential in the design of affordable high-speed optoelectronic devices, although we are aware that we are still at an early stage in achieving these goals.