Controllable Synthesis Of TiO₂Hierarchical Structures And Their Application In Quantum Dot Sensitized Solar Cells

QDSSC is a novel optoelectronic device with low cost, stable performance, simple production process.Therefore, QDSSC has attracted extensive research attention. Photoanode film is the heart of QDSSC, thestructure and producing method decided the final conversion efficiency of QDSSC. An ideal photoanodematerial should have follow qualities:1. high surface area for high QDs loading capacity;2. high scatteringeffect;3. Efficientive charge transfer channel to improve the electron diffusion rate. The major works are:(1) TiO2hierarchical (THSs) composited of ultra-thin nanosheets exposing high percent (001) facetswere successfully prepared via a one-step hydrothermal method. The time-dependent trails indicate thecrystal growth of the THSs experience an interesting self-assembling process. Thanks to their structuraladvantages, when used as the photoanode material in quantum-dot sensitized solar cells, a powerconversion efficiency of3.47%was demonstrated, which indicate~25%improvement compared with thenanoparticle cells (2.75%).(2) Hexagonal prisms TiO2hierarchical structure were synthesized by hydrothermal method usingtetrabutyl titanate as precursor under the mediation of HF. Anatase TiO2hierarchical structures withhexagonal prisms, tubes and tube/nanoparticles hybrid primary architectures were selectively prepared byaltering the dosages of TBT. Three types of photoanodes were prepared by mixing50%nanoparticles withthe above mentioned products, and a nanoparticle photoanode was also used for comparison. The QDSSCbased on hierarchical structure composed of tube/nanoparticles could well balance the QDs adsorption andthe electron transport, which results in a higher conversion efficiency of3.86%, indicating a~39%improvement than the nanoparticles based QDSSC.(3) TiO2mesoporous microspheres with quasi-single crystal structure and higher crystalline wereprepared via a facile hydrothermal method. The size of mesoporous spheres (~100,~200,~300and~1000nm) can be tuned by simply adjusting the TBT dosages. The mesoporous structure TiO2photoanodehave better scattering effect and lower election recombination, which permits a better conversion efficiencycompared with the nanoparticle based cell. Moreover, the QDSSCs compared of~300nm mesoporous spheres achieved in the highest conversion efficacy of3.10%.