In the present framework, the TiO2 thin film at different thicknesses (where d = 100, 120, 140, 160, 180, and 200 nm) has been successfully synthesized using the well-known thermal evaporation technique. The thickness of TiO2 layer has been monitored utilizing the quartz crystal monitor (type-FTM4, Edwards). The effect of TiO2 film's thickness on the structural, optical, electrical and photovoltaic properties has been investigated. The structural parameters of TiO2 layer such as the lattice strain, ε and the crystalline size, D have been computed utilizing the XRD pattern. According to the results of the XRD, it has been found that the crystalline size has been increased while the lattice stress decreased as the thickness of the TiO2 layer increased. The results of SEM have been shown that as the TiO2 film's thickness increases, the grain size improves. On the other hand, the values of the optical bandgap decreases as the thickness of the film increases. The energy diagram of TiO2 layer and also for the fabricated solar cell have been plotted. The capacitance-voltage (C-V) characteristics have been studied to determine the type of the heterojunction (sharp or gradual). According to such measurements, the built-in-voltage, the width of the depletion region, and the maximum electric field have been extracted. The polarization dependence of an electric field has been investigated. As well, the significant influence of TiO2 layer on optimizing the performance of the TiO2/p-Si solar cell has been also studied. The dark and illuminated current density-voltage (J-V) characteristics for the fabricated solar cell has been studied. The Ohmic, SCLC regions and the transition voltage have been determined. The parameters of the TiO2/P-Si solar cell such as the rectification ratio, RR, the junction resistance and the parasitic resistances have been studied. Furthermore, it has been found that the power conversion efficiency PCF and the fill factor FF of the heterojunction have been increased with increasing the thickness of TiO2 layer. Finally, the temperature dependence of the open-circuit voltage (VOC) has been studied to estimate the activation energy as a function of the thickness of TiO2 layer in the fabricated system.
