Molarity-Driven Modulation of Li2O Thin Films for UV-Sensitive Photovoltaic Devices

Li2O powders were synthesized by the sol–gel method using lithium nitrate solutions of 1.0 M, 0.9 M, and 0.7 M to analyze the effect of precursor concentration on photovoltaic and optical properties. Reflux heating, filtration, and calcination of the samples were followed by analysis through UV–VIS spectroscopy. Optical properties such as absorption coefficient, extinction coefficient, and band gap were determined, and the band gap increased with increasing concentration from 3.410 eV to 3.573 eV. The powders were pasted and coated onto FTO substrates, sensitized by Blue Nile dye, and packaged with graphite-coated counter electrode and iodine electrolyte. I–V measurements under illumination of 0.55 W·m−2 showed the 1.0 M sample reached maximum efficiency (0.903%), resulting from the stronger absorption and narrower band gap of the sample. Films with lower concentration had decreased photovoltaic performance. These findings show that Li2O content significantly impacts optical properties and solar cell efficiency, offering a direct route to improving Li-based material performance in low-light photovoltaics.