Towards all-inorganic antimony sulphide semi-transparent solar cells

NiO, a wide band gap hole-transporting material (HTM), is gaining attention in photovoltaics due to its optical transparency, chemical stability, and favourable band alignment with absorber. This study uses NiO _x nanoparticle-based HTM in semi-transparent Sb ₂ S ₃ solar cells via a simple chemical precipitation method. We optimized NiO _x layer by varying precursor solution concentration and studied its impact on optical and structural properties, composition of nanoparticles and subsequent effect on the performance of semi-transparent Sb ₂ S ₃ solar cell. NiO _x nanoparticles, deposited from nickel(II)nitrate hexahydrate (precursor solution concentrations of 0.2 M to 1.2 M), were thermally treated by two steps at 90°C for 6 h and 270°C for 3 h. Nanoparticles with crystallite sizes of 6–9 nm had band gaps (Eg) of ca 3.65–3.70 eV. Using 1.2 M concentration yielded the largest crystallites (9 nm), lowest Eg (3.65 eV) while retaining the most organic residues. The highest power conversion efficiency (2.65%) was achieved with NiO _x from a 0.5 M precursor, a 60% improvement over HTM-free cells. The effect of precursor solution concentration on the solar cell parameters (efficiency, fill factor, open circuit voltage and short circuit current) are discussed. Present work paves a path toward stable, efficient, and cost-effective all-inorganic Sb ₂ S ₃ solar cells using NiO _x HTM instead of organic counterparts.