Environment of TiO$_{2 }$ nanoparticles as an important factor to achieve highly efficiency on dye sensitized solar cells*

Amorphous TiO2 nanoparticles were synthesized by sol gel technique. Environment of nanoparticles was neutralized by ammonia, and pH5.8 of TiO2 gel was achieved in result, which is close to the point of zero charge (PZC) of anatase TiO2. Highly interconnected, mesoporous, transparent films were fabricated from the TiO2 colloid with pH5.8. AFM, SEM XRD analyses were carried out for the investigation the size of nanoparticles, the surface morphology and the crystal structure of films. Volt-amperic characteristics showed an improvement in the cell efficiency along with the increasing of pH TiO2 colloid. The cells parameters (Voc, FF, Jsc, $\eta )$ were studied depending on the pH of TiO2 colloid. Increasing pH of the colloid from 2.1 to 5.8 enhanced the overall conversion efficiency of the dye-sensitized solar cells by approximately 30{\%} , and 9.2 {\%} of efficiency was achieved with N719 dye under illumination by simulated AM1.5 solar light (100 mW/cm-2).