Photoelectrochemical Performance Of ZnO And TiO₂ Nanostrctre Sensitized Solar Cells

Sensitized solar cells have become a hot spots in the field of clean and renewable energy becase of their low cost,simple preparation process and high energy conversion efficiency.This paper focses on the constrction and modification of electron-condcting materials in solar cells.Respectively,the nanostrctres based on ZnO and TiO₂ to bild qantm dots sensitized solar cells and dye-sensitized solar cells,from the interface modification,nano-strctre control,ion doping and other aspects of the electrode to effectively reglated microstrctre and cell of performances.The main contents are as follows:The ZnO nanorod arrays were prepared by two hydrothermal methods,and the ZnS passivation layer was sccessflly introdced on the srface of the ZnO nanorod arrays by sccessive ionic layer adsorption and reaction,which effectively prevented the corrosion of ZnO electrode from the qantm dot photosensitizer of CdS,The ZnO/ZnS/CdS nanorod arrays doble-shell qantm dot sensitized solar cells were obtained.By adjsting the thickness of CdS nanocrystals,the photoelectric conversion performance of the cell was optimized,and the photoelectric conversion efficiency of 1.75%was achieved.Althogh the qantm dot-sensitized solar cells have advantages in band gap control,preparation process and cost,their complex interface strctres are difficlt to be precisely controlled,leading to the cell efficiency has been stagnant,and with the development of rthenim dyes,dye sensitized solar cell has made rapid progress.One-dimensional nanorods have a direct electron transport channel,which has a great advantage in the rapid condction of electrons in dye-sensitized solar cells.For this reason,based on the research of ZnO nanorod arrays,ZnO nanorod arrays as a electrode was fabricated,N719 as a sensitizer,with a cell efficiency of 0.5%.The mlti-layer ZnO nanorods with nanometer flowers on the srface of nanorod array were obtained by sing several hydrothermal processes,and the specific srface area and the amont of dye adsorption were increased.When the thickness of the film with 56.7?m,the optimm photoelectric conversion efficiency of ZnO mltilayer photoanode was 1.8%,.Althogh the efficiency of the modified ZnO nanostrctres is improved,however,compares with the crrently widely sed TiO₂ nanoparticle film anode,we still have a large distance in the cell efficiency,which may be de to the following reasons:1)the carrier transfer rate is not high on ZnO nanorods;2)The specific srface area of the photoanode is not high enogh compared with the particle system;3)the photo-generated carriers generated by the excited state dye molecles are difficlt to be injected into the photo-anode rapidly.In view of the above problems,we condcted a frther research separately.In order to improve the carrier condction rate,we se n-type doping,and commonly sed Li⁺ doped ZnO film,de to the atomic radis of Li element is small,it is easy to exist in the gap-type magazines of ZnO crystals,so as to introdce n-type dopant into the ZnO semicondctor to increase the carrier mobility.Effectively improves the carrier transmission rate in the ZnO photoanode,also redees the transmission resistance of ZnO/electrolyte interface,and inhibits the composite of the carrier at the interface,When the concentration of Li+ is 0.01 M,the energy conversion efficiency of the assembled dye-sensitized solar cell is increased to 4.25%.Althogh the efficiency of ion-doping of the photoanode is greatly improved,the efficiency of carrier injection into ZnO is still difficlt to be improved.The reason may be that the N719 dye is based on the traditional TiO₂ nanoparticles development?electron injection efficiency in TiO₂ close to 100%?.the complex of ZnO²⁺/N719 is easily formed,which is not condcive to the electron transfer in ZnO.ZnO,TiO₂,TiO₂/ZnO and TiO₂/ZnO/TiO₂ composite nanostrctrs are prepared by soltion method,the experimental reslts show that the photoelectric properties of the cells is TiO₂>TiO₂/ZnO>TiO₂/ZnO/TiO₂>ZnO,It is confirmed that the photocarrier cold be injected more qickly in TiO₂ nder the condition of sing N719 dye,ZnO had a better electron mobility,bt the electron injection efficiency decreased,the interfacial recombination of carriers exists at the interface between TiO₂ and ZnO in the composite granlar film,and the cell performance is still affected.The cell efficiency is optimized by adj sting the thickness of the TiO₂ film the photoelectric conversion efficiency is 9.92%when the film thickness is 29.4 ?m.Becase the extinction coefficient of TiO₂ is not high enogh,in order to avoid the loss of light energy existing in the photoanode attached dye,TiO₂ sbmicron particles are introdced into the srface of TiO₂ nanoparticles to enhance the scattering of light and the tilization of light rate in the photoanode.the thickness of the nanoparticles is 21.2 ?m,and the energy conversion efficiency of the cells is the best?10.3%? with the TiO₂ particles of 400-500 nm as the scattering layer.The short circit crrent is 18.72 mA/Cm,the open circit voltage is 0.8 V and the filling factor with 67.89%.