Towards all inorganic antimony sulphide semitransparent 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 Sb₂S₃ solar cells via a simple chemical precipitation method. We optimised 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 Sb₂S₃ 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 precursor residues. The highest power conversion efficiency (2.68%) 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 Sb₂S₃ solar cells using NiO_x HTM instead of organic counterparts.