Preparation Of Small Size Four Needle NaNO-ZnO&Its Application In Solar Cells

In order to deal with the global fossil fuel depletion and the accelerated surging global demands for energy, the renewable energy will gradually replace the conventional fossil fuel energy.ZnO is a direct transition, wide band gap material (Eg=3.37eV), and ZnO has high exciton binding energy (60meV) and the characteristic of piezoelectric, conductive, transparent in the visible range and high reflectivity in the infrared. Therefore, ZnO has widely used, such as the transparent electrode of LCD or LED, photovoltaic, chemical sensors, ferroelectric memory, heat reflector, surface acoustic wave devices and low loss waveguide, etc.At present, according to the technology, the solar cells is mainly divided into silicon solar cell, cadmium telluride (CdTe) solar cells, copper indium gallium selenide (CIGS) thin film solar cells, III-V compound solar cells, organic solar cells and dye-sensitized solar cells (DSSC), etc.In this paper, based on the previous methods, we creatively invented a method of preparating the small size four needle nanometer ZnO with the diameter below20nm, further, we had greatly improve the yield of the small size four needle nanometer Zinc Oxide. In the paper, we used the X ray diffraction (XRD), scanning electron microscopy (SEM), and the characterization method of PL characterization, UV Vis spectra to characterize the small size four needle nano ZnO samples. According to researching the different influences of the different process parameters, we discussed the mechanism of the small size four needle nanometer ZnO’s formation, which result in the optimal conditions for preparing the small size four needle nanometer ZnO.Then, in this paper, we prepared ZnO-quantum dot solar cells by using the ZnO with CdTe, CdSe, CdS and PbS quantum dot. On the other method, we used N719to sensitizing the ZnO and assembled the dye sensitized solar cells (DSSC). On the third method, we used the ZnO and the vinylene derivatives of poly [2-methoxy,5-(2-ethyl-Hexyloxy)-phenylene vinylene](MEH-PPV) to assembled the double-layer of inorganic/organic structure surface heterojunction polymer solar cells. Further more, we used the solar cell testing system (A500W xenon lamp as the sun simulator, the electrical signals output by CHI660D electrochemical workstation) to test the ZnO-CdTe, ZnO-CdSe, ZnO-CdS, ZnO-PbS solar battery, dye sensitized ZnO solar cell and ITO/Au/ZnO/MEH-PPV/PEDOT:PSS/ITO solar cell.The results show that:(1) The temperature of zinc evaporation is the key factor that affects the morphology and the size of the four needle nano ZnO. The evaporation temperature of zinc is higher, the size bigger.(2) In order to obtain high-yield and good crystal, the key is to control the reaction system containing without the influencing molecules in the main reactions of2Zn (g)+O2=2ZnO (g), such as water, or else substances which will influence the crystal morphology of the ZnO.(3) The ZnO XRD spectra prepared by dry chemical vapor deposition (DCVD) are consistent with the standard card of No.36-1451JCPDS card in diffraction peak position and intensity of diffraction peak, which indicating that the generation is very high purity six wurtzite with the lattice constants are a=0.32421nm, c=0.51941nm.(4) The SEM characterization results show that, under the evaporation temperature of450℃, the small size four needle nanometer ZnO’s needle diameter is approximately15nm and the needle length is about200nm, which is the minimum size of the nano ZnO prepared by vapor phase deposition method throughout the world by now.(5) The characterization of PL results show that, due to the smaller size, the ZnO has effective absorbed light and exciton transition position in visible light of466nm, where the green excition position is moving towards blue and the excition intensity is stronger, which will be conducive to form a higher effective electron-hole in the photovoltaic devices which used the small size four needle nanometer ZnO.(6) The characterization of UV Vis spectra showed that the small size four needle nanometer ZnO size is smaller, and the crystal structure is more regular, which resulting in the UV-visible absorption band range wider and the absorption strength greater.(7) Under the similar other conditions, the ZnO size smaller, the Eff of the solar cell prepared by the ZnO highher, which is coincide with the theory of the size smaller, the small-size-effection more significant.(8) Under the similar other conditions, the order of the Eff of the solar cell prepared by the ZnO and different quantum dots is:CdTe>CdSe>PbS>CdS.