Potassium-doped Zinc Sulphide (K:ZnS) nanostructured films were deposited on silica substrates using a colloid-based solution method, with varying thicknesses from 3 to 6 coats. The films exhibited p-type electrical conductivity and favorable optical properties for ambipolar and optoelectronic device fabrication. X-ray analysis confirmed a polycrystalline cubic phase in all the films, with crystallite sizes of 7–27 nm. Scanning electron micrographs revealed spherical globular grains of sizes 1.20–2.84 μm, leading to improved compactness with thicker films. UV/VIS analysis demonstrated a red-shifted band gap with increasing thickness. Photoluminescence under UV excitation revealed a peak at 477 nm attributed to K-induced trap levels. The electrical resistivity (1.34–6.00) × 102 Ω⋅cm, carrier concentration (4.63–13.33) × 1015 cm−3, and mobility (2.25–3.50) cm2/V·s varied with film thickness. The minimum resistivity of 1.34 × 102 (Ω⋅cm), maximum conductivity of 7.46 × 10−3 (Ω−1⋅cm−1), and highest mobility of 3.50 (cm2/V·s) were obtained for K:ZnS-6 film.