<p>This study successfully prepared Zn₂SnO₄ and potassium-doped Zn₂SnO₄ films using an economical spray pyrolysis at 350&#xa0;°C. The XRD study of potassium-doped Zn₂SnO₄ layers presents a polycrystalline cubic crystal structure. Examining the structural properties reveals that increasing potassium content reduces crystallite size while concurrently increasing dislocation density and lattice strain. The optical characteristics of Zn₂SnO₄ and potassium-doped Zn₂SnO₄ films were analyzed, and it was shown that the refractive index of the potassium-doped Zn₂SnO₄ films increased with increasing K ratio. Furthermore, the study of the optical transitions of the investigated samples revealed a direct transition, and the optical energy gap decreased with increasing potassium concentration. In addition, optoelectrical parameters have been thoroughly investigated, including relaxation time, optical electronegativity, plasma frequency, electrical conductivity, and optical conductivity. Likewise, the values of nonlinear optical parameters for the potassium-doped Zn₂SnO₄ layers were enhanced by boosting the potassium concentration. The results indicate that these films are wide-bandgap semiconductors, suggesting their suitability for various solar cell applications as window layers. The electrical results confirmed that the Zn₂SnO₄ and K-doped Zn₂SnO₄ films exhibit n-type semiconductor characteristics as determined by hot-probe measurements. The ideality factor (<i>n</i>) of the explored Al/ K-doped Zn₂SnO₄/ P-Si/ Al heterojunction diminished as the potassium content increased. Furthermore, the <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\({\phi}_{b}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>ϕ</mi> <mi>b</mi> </msub> </math></EquationSource> </InlineEquation> of the investigated heterojunction is enhanced as the potassium concentration rises from 2 to 8 wt.%. The motivation for this work is to explore cost-effective, efficient strategies for tailoring the functional properties of Zn₂SnO₄ thin films, as this material is widely regarded as a promising n-type semiconductor for optoelectronic applications.</p>