Preparation And Characteristics Of Dye-Sensitized Nanocrystalline TiO₂ Porous Film Photoelectrodes

Energy crisis and environmental pollution are greatly challenging human beings in the 21st century. The application of solar energy is the most effective means to solve these problems. Dye-sensitized Solar Cell (DSC) has attracted much attention as a novel photoelectrochemical solar cell based on low-cost, simple technique and stable character.In this dissertation, the DSCs with overall conversion efficiencies over 8% were attained under illumination of simulated AM1.5 sunlight (light intension 376W/m2) by means of substrate electrodeposit pre-treatment, TiCl4 post-treatment, blending sol with larger TiO₂ particles, using of TiO₂ nanotube and nanorod and reducing the resistance of substrate.TiO₂ nanoparticles sol was fabricated by the hydrolyzing alkoxide method. After concentrating the sol and adding PEG, TiO₂ paste was gotten. The paste was coated onto the substrate by screen-printed method then sintered at 450℃for 0.5h. Then the TiO₂ mesoporous electrode was prepared. The influences of PEG quantity on the film morphology and the photo- electric conversion efficiency are investigated as well as influences of the electro-deposit pretreatment, mixing with larger TiO₂ particles and TiCl4 post-treatment on photo-electric conversion efficiency. The better overall conversion efficiency 4.33% is gained through optimization of different treatments.Titania nanotubes were synthesized from P25 nanopowder using the hydrothermal method. The structure and phase of the nanotubes were proved after sintered at 400℃and 450℃for 1h respectively. Nanotubes is still retained tubular structure by sinterring at 400℃and changed into nanorods by sinterring at 450℃. Nanotube composite electrodes were gotten by blending nanotube with the TiO₂ paste from DYESOL in different ratios. The composite electrode with an active area of 1cm2 and the ratio nanotube to particle is 1:1 showed obviously higher overall conversion efficiency (8.22%) than that of electrode using TiO₂ paste from DYESOL (4.64%). Nanorod composite electrodes were also gotten by blending nanorod with P25 from Degussa in different ratios, but their performances did not improve much more than that of P25 electrode.The I-V properties of DSC are analyzed through the equivalent circuit in direct current mode. The influences of series resistance (Rs) and the shunt resistance (Rsh) on the performance of DSCs are qualitative discussed. By simulating the I-V curve in the case of different Rs, the effects of Rs on open circuit voltage (Voc), short circuit current (Isc) and fill factor (FF) are obviously represented provided that Rsh equals to∞. The effects of Rsh are represented too provided that Rs equals to zero. By using different substrates such as ITO, FCO and silver rims printed on the substrates, different Rs are gotten. These substrates are used for DSCs, the influence of different substrates on Voc, Isc and FF are analyzed and compared with the simulated case. By using the FCO substrate printed with silver rim, a N719 sensitized solar cell have an overall conversion efficiency of 8.01%. When use 2,9,16,23-tetracarboxy zinc phthalocyanine to sensitize the same electrode, The solar energy conversion efficiency (η) 0.381% with Isc 0.409mA/cm2, Voc 525mV and FF 0.672 was attained.