Undoped thin films of cupric oxide have been prepared by a simple chemical spray technique. Obtained samples were mostly polycrystalline and p-type semiconductor. Thermopower of a set of as-deposited samples with thickness between 340 and 620 nm have been measured in the temperature range 300-450 K. The thermovoltages were found to change sign with thickness. The dominating carrier scattering process that can limit the electrical conductivity or the Hall mobility values at room temperature may be the lattice phonon scattering. The observed variations of the position of Fermi level with the film thickness have been qualitatively explained invoking the principle of modulation of the acceptor density profile by the density of donors during the time of growth of film.