Herein, indium doped tin oxide (ITO) nanoparticles were produced via co-precipitation process and used to develop a photodiode (p-Si/n-ITO) via a cost-effective spin coating process. X-ray diffraction (XRD) study revealed a mixed crystalline phase of tetragonal and cubical structures for the doped samples indicating nanocomposite formation. The effect of indium ion vibrations of OH bonds is observed by Fourier transform infrared (FTIR) spectra. The fine nanoparticles (NPs) synthesis was confirmed by SEM and NPs are of spherical shape confirmed via TEM. The maximum absorbance 262 nm and minimum optical band gap Eg = 2.8 eV was attained for 5 wt.% of In. From electrical studies, the conductivity was found to be in the range 1.4767 × 10−6 and 0.74 × 10−13 S/cm. The p-Si/n-ITO diode was fabricated with 5 wt.% of In and its ideality factor (n), barrier height (Φb), photosensitivity (PS), responsivity (R) and specific detectivity (D*) were examined in dark and light surroundings. The diode exhibited good Ps = 21% and D* = 3.38 × 107 Jones. The output results indicate that the developed device will be good in optoelectronic devices.