The Controllable Synthesis Of Tin Dioxide Nano Structure And The Application In Quantum Dot Sensitized Solar Cells

Quantum-dot Sensitized Solar Cell(QDSSC) has received extensive attention due to its low cost and high power conversion efficiency. As an important part of QDSSC, photoanode not only support the quantum dots(QDs), but also separate and transport the photoelectron. Generally, the ideal optical anode materials should have a large specific surface area, good light harvesting and electron transport efficiencies. Compared with the traditional anode materials, SnO2 has higher electronic diffusion coefficienct and more negative conduction band position, which can match with a variety of semiconductor quantum dots. In order to improve the performance of photovoltaic devices, one-step hydrothermal process was used to prepare various SnO2 structures and adopted as the photoanode for QDSSC. In addition, growth mechanism of SnO2 structures and their influencing mechanism on the performance of the QDSSC were studied in detail. The main research contents of the article are listed as follows:(1) An in situ deposition technique is developed to prepare green Ag/Ag2 S quantum dots sensitized SnO2 photoanode for solar energy conversion. An impressive high photocurrent density(Jsc) of 26.0 mA·cm-2 is demonstrated in a device using polysulfide S2-/Sn2- as electrolyte and Cu2S/brass as counter electrode. Based on the optical and electrochemical investigations, the greatly improved Jsc is attributed to both the plasmon induced absorption enhancement of Ag2 S and the direct hot electron injection through the SnO2/Ag interface.(2) Tin dioxide hierarchical nanocrystals were prepared through a one-step hydrothermal method with n-butyl alcohol as solvent and stannous chloride as precursors. By adjusting the reaction time to research the growth mechanism of the nanocrystalline, we found that the as-prepared hierarchical structure is composed of primary nanocrystalline by means of oriented assembly Ostwald ripening. When used as the photoanode in CdS/CdSe QDSSC, the hierarchical nanocrystals with larger specific surface area and pore diameter can improve the adsorption quantity of quantum dots sensitizer. Moreover, owing to the oriented structure in the membrane structure, the interface and the crystal lattice defects were decreased, which improves the transfer efficiency and reduced the charge recombination.. Thanks to this structural advantageous, the efficiency achieved to ~ 3 %, which is greatly enhanced compared with the nanoparticles based QDSSCs.(3) SnO2 hierarchical microspheres were prepared Using ethanol/water mixture as the reaction system and stannous chloride as precursors. By changing the reaction time, the formation of hierarchical microsphere consists nucleation, growth, assembly, and repening processes. By changing the alcohol/water ratios and hydrochloric acid dosages, different SnO2 hierarchical structures, such as solid microspheres and hollow microspheres were prepared, indicating the ethanol and hydrochloric acid could influence the formation of the hierarchical SnO2 structure. When using the hierarchicalstructures as the scattering layer material of the CdS/Cd Se QDSSC, due to the excellent light scattering effect, the short-circuit current density was greaty inproved, which leads to higher conversion efficiency the nanocrystals based devices.