Development of CdSe, Sb2Se3, and Sb2S3 Layers for Next-Generation Thin-Film Solar Cells

This research project investigates the growth, characterisation, and optimisation of semiconductor materials critical to next-generation thin-film solar cell devices. The study focuses on CdSe, Sb₂Se₃, and Sb₂S₃ chalcogenide materials, aiming to advance their applications in graded bandgap photovoltaic (PV) devices. Comprehensive experimental concepts were developed and implemented. The semiconductor thin films; CdSe, Sb₂Se₃, and Sb₂S₃ were successfully fabricated on conductive glass/FTO substrates via electrodeposition technique. Advanced characterisation techniques, including photoelectrochemical (PEC) measurements, X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, and energy-dispersive X-ray spectroscopy (EDX) were employed to analyse the structural, optical, and electrical properties of the materials. CdSe thin films were electrodeposited from an electrochemical bath at potentials between 1500 mV to 1900 mV, exhibiting n-type and p type conductivities, with energy bandgaps ranging from 1.70 eV to 1.88 eV respectively. Post-deposition heat treatments enhanced crystallisation, producing high-quality polycrystalline films with mixed hexagonal and cubic phases. Sb₂Se₃ films were electrodeposited between 1600 mV and 1950 mV at ~85°C, demonstrated optical energy bandgaps of 1.08 eV to 1.68 eV with p-type and n-type conductivities. Heat treatments improved crystallinity, yielding polycrystalline layers with orthorhombic structures. Raman spectroscopy confirmed the dominant peaks as Sb₂Se₃, while SEM revealed large grains up to 5 µm, critical for light absorption. Sb₂S₃ thin films were grown in a highly basic environment at potentials between 1500 mV and 1900 mV, exhibited optical energy bandgaps from 0.50 eV to 1.03 eV after annealing. The films demonstrated orthorhombic crystallinity and promising optoelectronic properties suitable for use as window material in PV devices. Several challenges were reported during the cause of the research. Despite these obstacles, significant progress was achieved in optimising deposition parameters for each material, contributing valuable insights into understanding properties of CdSe, Sb2Se3 and Sb2S3 semiconductor materials. While reportable device fabrication could not be realised within the timeframe, the groundwork laid by this research offers a robust foundation for future studies. Additional supporting results are provided in the appendix section. These results include characterisations used to corroborate key interpretations, clarify analysis, and provide further context. Keywords: Electrodeposition, characterisation, Glass/FTO, Cyclic voltammetry, Optical absorption, PEC, XRD, SEM/EDX.