Preparation And Research Of ZnO Based Dye Sensitized Solar Cells

Dye sensitized solar cell is a new type solar cell. TiO2 used as photoanode in DSSC is widely studied due to its extensive source and stable chemical property. The efficiency of DSSC based on TiO2 has achieved 13%. Compared with anatase type TiO2 of anatase type, the energy gap of ZnO differs by 0.15eV, which is 3.37eV, at room temperature. However, the electronic migration rate in ZnO photoanode is apparently higher than in TiO2 photoanode. ZnO becomes the most studied material in DSSC photoanode in addition to TiO2 owing to its simple preparation, plentiful morphology and easy controllable process at low temperature, in this paper, the study of ZnO-based DSSC was as following(1) ZnO powder was prepared by carbon template method. The effects of molar ratio of Zn/C and hydrothermal temperature on the morphology of ZnO were mainly studied. The spherical structure remained well and nanorods grew on some ZnO surface when the Zn/C molar ratio was 2:1. it is 2 microns in diameter, nanorods growth a part of the ball surface, the diameter of the nanorods was 20 nm, length is 200 nm, length to diameter ratio of 10:1. When the temperature below 160℃, the polymerization reaction was hard to react, resulting in obtaining ZnO nanoparticles. When the temperature over 220℃, the concentration differential was too large, leading to a fast polycondensation in some parts and a serious agglomeration. The optimum hydrothermal reaction temperature to prepare ZnO with microsphere structure was 180℃.(2) ZnO powder prepared by carbon template method was applied in DSSC. when the Zn/C molar ratio and hydrothermal reaction temperature were 2:1 and 180℃, the performance of the DSSC fabricated by ZnO powder prepared by reacting for 4h was optimum. The possible reason was ZnO provided a large surface and the nanorode on the surface had a higher electron mobility. The Voc,Jsc,FF and PCE of the cell were 0.62 V、14.96 mA/cm2、0.63 and 1.91%, respectively. The electronic life was 33.53 ms.(3) ZnO microsphere with hierarchy structure was preprared by alcohol hot refluxing method. The effects of slurry preparation process, rate of temperature increase and thickness of photoanode ect on the properties of the DSSC were mainly studied. hierarchy structure would be destroyed by milling while remain intact by vortex method. the temperature increase rates of 3℃/min、4℃/min and 5℃/min merely had influence on the properties of DSSC. The increasing of thickness of film would not only result in a higher dye loading amount but also lead to a longer transfer path which would give rise to a easier electron recombination, restricting the diffusion of electron. when milling for 3h, and sintering at 450℃ for 60 min with a temperature increase rate of 3℃/min, the DSSC assembled by photoanode with a thickness of 20 μm achieved an optimum efficiency of 3.39%. the Voc, Jsc and FF were 0.60V、 8.66mA/cm2 and 0.64.(4) ZnO nanorod based on ZnO microsphere by alcohol thermal method was prepared. The effects of the concerntration of growth solution and growth time on the ZnO sphere/nanorod composite film were studied. The diameter first increased from 20nm to 30nm and finally to 50nm with the concerntration of growth solution first increasing from 0.01M to 0.02 and finally to 0.04M. The lenth of nanorod first increased from 200nm to 800nm and finally to 1000nm with the grow th time first increasing from 15h to 30h and finally to 65h. the ZnO microsphere/nanorod composite photoanode, counter electrode and electrolyte were assembled into DSSC. The DSSC fabricated by composite powder prepared at the condition of 0.05M growth solution and 30h growth time showed an optimum efficiency. The efficiency, Voc, Jsc and FF were 3.51%、0.52V、12.78mA/cm2 and 0.51.