NiOₓ nanoparticles as HTM in semi-transparent Sb₂S₃ solar cells

This work contributes to the development of fully inorganic photovoltaics by the construction of semi-transparent Sb₂S₃ solar cells that employ NiOₓ nanoparticles as the hole-transport material (HTM), through the optimization of both nanoparticle preparation and device fabrication parameters. NiOₓ powders were synthesized by chemical precipitation and annealed at controlled temperatures; XRD, FTIR, XPS, and UV–Vis analyses showed that higher annealing improves crystallinity and reduces residues, identifying 500°C as the optimal compromise between electronic/optical quality and thermal input. Devices with a stacked thin-film architecture (glass/FTO/TiO₂/Sb₂S₃/NiOₓ/Au) were created, revealing that the choice of dispersant and the HTL thickness govern film uniformity and, in turn, device performance; isopropanol and the deposition of five drops yielded the most favorable results. Post-deposition annealing of the NiOₓ HTL was also examined, indicating that 180 °C for 15 minutes in air reduces surface defects and repairs the crystal structure, thereby improving charge transport and suppressing recombination without inducing thermal degradation. Finally, studies on NiOₓ ink filtration indicated a slower degradation for unfiltered inks, plausibly due to a higher surface packing density that limits moisture ingress, while average visible transmittance measurements confirmed the preservation of semi-transparency. Overall, the results elucidate process-structure-property relationships that enable a balance between efficiency and transparency, positioning NiOₓ as a viable HTM for stable, architecturally integrable Sb₂S₃-based photovoltaics.