The influence of substrate and post-annealing temperature steps on the unique physical, structural, morphology and optical properties of CdTe thin films deposited by a non-vacuum spray process were investigated for solar cells. Scanning electron microscopy (SEM) and X-ray diffraction spectrometer (XRD) were employed to study surface morphologies and structural changes, respectively. It was observed that CdTe films produced at substrate temperature of 130 degrees C had substantially larger grain size and showed denser morphology. Annealing at 130 degrees C-330 degrees C in air caused small grains throughout the surface at random. Annealing at 430 degrees C, however, initiated fusing between grains and produced uniform morphology with an average grain size of about 60 nm. XRD analyses showed that CdTe films deposited at 130 degrees C and then post-annealed at 430 degrees C behaved in the originally strong (111) direction without the formation of secondary CdTeO3 phase. Optical band gap measurements indicated that the values of CdTe films grown at 130 degrees C and post-annealed at 430 degrees C in ambient condition were about 1.45 eV. All results exhibit 130 degrees C and 400 degrees C to be critical deposition temperature and heat treatment temperature at which physical, optical and structural properties of CdTe thin films start to change.