The Impact Of TiO₂ Morphology On Photoelectric Performance Of Dye-sensitized Solar Cells

The crisis of energy and pollution of environment have become a dilemma for the human with the flourishing global economy and increasing human activities. To change this situation, the development and study of new energy such as solar energy is a matter of great urgency. Dye-sensitized solar cells(DSSC) with low cost, high photovoltaic efficiency and environment protection have been paid great attention as the effective photovoltaic device to utilize the inexhaustible solar energy. The photoanode play an important role in DSSC, such as the adsorption of incident light and transfer of photo-induced electrons. The efficiency of light utilizing and state of electron transfer and recombination decide the photovoltaic performance of DSSC. This work focuses on the design of double-layered photoanode based on TiO2 nanomaterials with different morphology such as one dimension(1D) or single-crystalline TiO2, the high light harvesting efficiency, fast electron transfer and low recombination rate result in the enhanced photovoltaic efficiency, mainly as follows:(1) The one dimension TiO2-PVP nanofibers are prepared through simple electrospinning method, and then the 1D TiO2 nanorods are obtained using annealing and grinding process. The DSSCs based on P25 nanoparticles/TiO2 nanorods(NPR), P25 nanoparticles/P25 nanoparticles(DNP) and TiO2 nanorods/TiO2 nanorods(DNR) photoanode are fabricated using doctor-blade method. Compared with the DNP and DNR DSSCs, NPR DSSC showed enhanced photoelectric performance: 8.03% photovoltaic efficiency, 15.7 mA cm-2 photocurrent density. This can be attributed to the follow reasons: P25 underlayer optimizes the contact in the composite film and ensures the effective adsorption of dyes; 1D nanorods overlayer improves the light harvesting efficiency of photoanode film and transfer of photo-induced electrons.(2) The single-crystalline TiO2 hollow nanoparticles(HNP) and 1D spindles(SP) are prepared through different hydrothermal method. The TiO2 hollow nanoparticles with the size of dozens of nanometers act as the underlayer of double-layered DSSC. Similarly, the 1D Ti O2 spindles act as the overlayer. We investigate the effect of hollow nanoparticles/1D spindles photoanode structure on the photovoltaic performance of DSSC. The photovoltaic efficiency of hollow nanoparticles/1D spindles DSSC is up to 8.65%, which is 25% higher than that of hollow nanoparticles/ hollow nanoparticles DSSC, and also far superior to that of spindles/spindles or conventional P25 DSSC. The improved photovoltaic performance is attributed to the synergic effects, i.e. the single-crystalline structure of HNP and SP favoring for rapid interfacial electron transport, the relatively large specific surface area of HNP for effective dye adsorption, and the 1D geometry of single-crystalline TiO2 spindles for direct electron transport pathway and strong light scattering effect.