A high-performance indium tin oxide (ITO) coating is key in fabricating an efficient photosensor. The manufacturing process of ITO is complex and time-consuming. Therefore, establishing a production technology that is fast and capable of application to large areas is essential. The dispersion of nanoparticles in the process has a considerable influence on the photoelectric properties of ITO films. The degree of dispersion also determines the existence of the secondary phase, which is harmful during application. In this study, we compared the effect of different dispersion parameters such as the ultrasonic power and type of dispersant on the properties of spin-coated ITO films, i.e., the interfacial zeta potential, extinction ratio, and electrical properties. The electrical properties of spin-coated ITO films were affected by oxygen vacancies and the uniformity of tin oxide doping. Using an ultrasonic crusher with an output power of 600 W (3 h) with D305 dispersant, we obtained ITO particles with a minor hydrodynamic diameter of 176 nm. The spin-coated ITO film comprising these particles had a resistivity of as low as 10−4 Ω·cm after suitable heat treatment and a carrier concentration of approximately 1020 cm−3. The electrical properties of the spin-coated ITO were satisfactory for its application on a photodetector. Finally, we proposed that the service life of a sensor can be evaluated by monitoring the variation of the friction coefficient.