Studies of doped and undoped nanostructured zinc oxide thin films for solar cell application

Abstract

newline Transparent conductive oxide (TCO) thin films have received considerable attention due to their applications in various electronic and optoelectronic devices. ZnO has been extensively studied for many applications, because the material is nontoxic, abundantly available, chemically and thermally stable, and biocompatible. In this research work we report studies on pure and doped ZnO nanostructures (NS), its fabrication and applications. Pure and doped ZnO thin films were deposited on glass substrate by chemical bath deposition (CBD) and spray pyrolysis method. Effect of Al3+ and In3+ substitution on the properties of ZnO was studied by XRD and UV-Visible for structural studied, SEM and TEM for surface morphology and DC resistivity measurements for electrical properties. XRD and SAED patterns reveal a polycrystalline wurtzite phase of the ZnO-NS. Different morphologies of pure and doped ZnO nanoparticles (NPs) have been studied with a SEM and a TEM. Compositional analysis by EDX showed that the ZnO-NPs synthesized by both the techniques were free from impurities. The optical transitions in polycrystalline ZnO have been studied by PL spectroscopy. UV-Visible study showed that ZnO films have high transmittance (gt80%) and wide optical band gap (~3.44 eV). The electrical resistivity for Al-ZnO (AZO) is found to be 3.77×102 and#937;-cm and thermal activation energy was 0.3 eV. Optical and electrical properties reveal that the synthesized films can be tailored for optoelectronic applications. The ZnO, AZO and IZO films deposited by spray pyrolysis onto TCO coated glass plates were tested for PEC performance in sulphide/polysulphide electrolyte. Various cell parameters were improved for Al and In-doped ZnO films. The current density-voltage (J-V) characteristics of Cu2O/ZnO, Cu2O/AZO and Cu2O/IZO n-p heterojunctions were tested. The AZO/Cu2O solar cell showed the power conversion efficiency as high as 1.96 %, which can be alternative for fabricating new solar cell device.