Preparation And Photoelectric Characterization Of Dye-sensitized La³⁺-doped TiO₂ Nano Crystalline Thin Films

Dye-Sensitized Solar Cell is one kind of Solar Cell that converts the light energy to electricity, with the advantages of low-cost, simple fabrication and no pollution to the environment, causing the interest of researchers from different nations on the study of Dye-Sensitized Solar Cell.In this paper, Sol-Gel method was applied to fabricate TiO2 nano-powder and the TiO2 powder was characterized by X-Ray Diffraction. TiO2 nano-porous films were prepared by screen printing method and spray coating method. And the microstructure and performance of three different thickness of TiO2 thin film is compared.La3+-doped TiO2 nano-powder materials were prepared by Sol-Gel method and were analyzed by X-Ray Diffraction. La3+-doped TiO2 nano-porous films were fabricated by spray coating technology to be the anode of DSSC, and were characterized by SEM and DSSC test system.The XRD results showed that the characteristic diffraction peaks of TiO2 by Sol-Gel method were consistent with the peaks of standard anatase crystal TiO2 when the La3+-doping concentration was controlled in the range of 0% to 1.0%. And the crystal structure of La3+-doped TiO2 remained the same one after doping. La3+ could partially replaces Ti4+ to form a oxygen vacancy, and it could also enter the lattice of TiO2 as a interstitial atom to form stable Ti1-3/4xLaxO2 solid solution. When the doping amount of La3+ is higher than 1.0%, the diffraction peaks of rutile TiO2 were found, and it can be concluded that doping La3+ would promote the transition of TiO2 from anatase phase to rutile phase, and both phases were existed to form a mixed crystal phenomenon. According to Scherder formula, when the doping amounts of La3+ were controlled in the range of 0.5% to 0.9%, the size of TiO2 particles could be within 10nm.According to the I-V curves of DSSC with the doping amount of La3+ by 0%, 0.3%, 0.5%, 0.8% and 1.0% respectively, the open circuit voltage stabilized around 0.6V when the doping amount of La3+ was above 0.5%. With the effect of La3+ doping, the short circuit current was increased significantly. As the doping concentration reached at 0.5%, the Jsc value of this DSSC was 5.5mA/cm2, and Jsc value would decrease gradually when the doping concentration was more than 0.5%. And the doping concentration of La3+ had a best value that is 0.5%. In this situation, the Voc, Isc and FF of DSSC are 0.608V, 5.500mA/cm2, and 0.576 V respectively. The photoelectric conversion could attain the value of 1.926%.