Abstract:
Photovoltaic efficiency relies on semiconductor properties. ZnO and Cu2O stand out as eco-friendly, abundant materials with tunable electronic traits, while their nanostructured morphologies unlock enhanced light absorption and charge transport, revolutionizing heterojunction solar cell performance. This thesis examines the fabrication and characterization of ITO/ZnO/Cu2O nanostructured p-n heterojunction solar cells. Using a sol-gel synthesis method, ZnO and Cu2O were synthesized from zinc and copper chloride precursors, ZnO prepared using 1-butanol, ethylene glycol, and sodium hydroxide, and Cu2O with 1-butanol, ethanol and sodium hydroxide. These nanostructures, deposited on ITO substrates via spin coating and annealed, exhibited distinctive morphologies: ZnO as nano flakes, nano rods, and nano spheres, and Cu2O as nano cashews, nano blocks, and nano jigsaw puzzles. Characterization techniques such as Field Emission Scanning Electron Microscopy (FESEM), X-ray Diffraction (XRD), and Energy Dispersive X-ray Spectroscopy (EDX) confirmed these structural and compositional attributes, showing high purity, crystallinity, and phase purity with ZnO in a wurtzite hexagonal structure and Cu2O in a monoclinic phase. Surface area emerged as a critical factor influencing photovoltaic performance. Brunauer–Emmett–Teller (BET) analysis identified ZnO nano flakes (26.858 m²/g) and Cu2O nano cashew shapes (3.9268 m²/g) as the highest-performing morphologies, significantly enhancing current density. These morphologies displayed superior conductivity ZnO nano flakes achieving 630.27 S/cm and Cu2O nano cashew reaching 253.49 S/cm highlighting the effect of structure on electronic properties. Optimized band gap values, derived from Tauc plot analysis and supported by SCAPS-1D simulation, identified a ZnO band gap of 3.2 eV and Cu2O at 2.13 eV as theoretically capable of 20.83% efficiency, underscoring a promising energy conversion potential. Despite these achievements, device fabrication encountered challenges, especially regarding the chemical instability of Cu2O, which oxidizes upon air exposure, hindering the realization of a complete current-voltage (I-V) curve. This limitation underscores the need for advanced, controlled-atmosphere fabrication methods such as multi-chamber deposition or inert processing environments to safeguard the Cu2O layer’s integrity. This thesis advances the field of oxide-based solar cells by establishing the essential role of nanostructure morphology, surface area, and stability in optimizing photovoltaic properties, laying a foundation for future work in sustainable solar energy solutions.