Fabrication and characterization of metal oxide nanostructured thin film for photovoltaic application.
Ukoba, Kingsley Ogheneovo.
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This study focused on fabrication and characterization of nanostructured metal oxide heterojunction solar cells for photovoltaic application. The study involved experimental fabrication of the device and modelling and theoretical validation of the fabricated device. The laboratory experiment was carried out by fabricating and characterizing nanostructured metal oxide thin film based solar cells using chemical spray pyrolysis and magnetron sputtering deposition techniques. The study included device design, materials tuning, process development, device characterization, device simulation, device reliability testing, and device circuit demonstration. The study covers the whole course of the device lithography and development. The spray pyrolysis method was used for depositing nickel oxide (NiO) thin films. Scanning electron microscope (SEM), energy dispersive X-ray powder diffraction (XRD), and Fourier transform infrared microscopy (FTIR) were used to characterize the films and four-point probe for the final device. Experimental optimization was conducted on the films with a focus on predeposition, deposition and post-deposition. The optimized result was used to fabricate a metal oxide NiO/TiO2 P-N heterojunction solar cell using spray pyrolysis and magnetron sputtering techniques. The optoelectronic properties of the heterojunction were determined. The fabricated solar cell exhibited 16.8 mA for the short circuit current, 350 mV open circuit voltage, 0.39 fill factor and conversion efficiency of 2.30 % under 100 mW/cm2 illumination. The result obtained from the experiment was compared and evaluated with the simulated results. The theoretical understanding of the device was modelled and theoretically validated. Theoretical understanding of the solar cell was established and thereafter the fabricated device modelled using solar cell analysis programs (SCAPxD). The working points used for the modelling included a temperature of 350 oC, illumination of 100mW/cm2, the voltage range of 0 volts to 1.5 volts. The output gave filled factor (FF) of 0.38 % which validated the experimental results. This study is a boosts in the quest to develop low-cost, environmentally friendly and sustainable solar cells materials and deposition method especially in developing and low-income countries that are experiencing electricity shortage using nanostructured metal oxide.