Fabrication Of Patterned Zinc Oxide Nanorod Arrays By Nanoimprint Technique And Investigation Its Photo-electric Properties

Nanostructures with light trapping effect have emerged as a promising route toward the highperformance solar cells and other optical devices. So fabricating of light trapping nanostructure withmodulating absorption properties to fulfill different design considerations of broadband absorption isdesirable. Nanoimprint technique is high efficiency, large-area, low-cost method for building smaller scale,more accurate nanostructures and nanodevices. In the nanoimprint process, the high cost of the imprintmold, limit the further application and development of nanoimprint lithography. The self-assembledpolystyrene microspheres（referred to as PS microspheres）is simple, low cost, and provides a simple andeffective technique for constructing highly order nanostructures.In this work, we take advantage of this ordered structure of PS microspheres as a template to build thePDMS stamp which is an effective solution for the stamps preparation. And then by using nanoimprintlithography hemispherical ZnO nanostructures with light trapping effect are fabricated. Functionalhemispherical ZnO nanorod arrays are prepared by low-temperature hydrothermal growth method.Throughcontrolling the growth temperature and concentration of the solution the period of the hemispherical ZnOnanorods array can be adjust easily. Finally, the optoelectronic properties of this structure and itsapplication in dye-sensitized solar cells are investigated. Specifically, the paper carried out works asfellows:1、Liquid self-assembled preparation of PS microspheres template which using PDMS stamp copyingthe surface structure of PS microspheres, nanodome arrays were prepared with PDMS stamp throughnanoimprint lithography. And then, a layer of ZnO seed layer was magnetron sputtered. By using thelow-temperature hydrothermal method ZnO nanorod arrays with different spacing were fabricated.Scanning electron microscopy (SEM), atomic force microscopy (AFM) and UV-visible (UV-Vis)absorption spectroscopy were used to study the morphology and optical properties of hemispherical ZnOnanorod arrays. The results showed that light-trapping effect in the visible region (450nm to640nm) wassuccessfully observed. By controlling the concentration and reaction time of the hydrothermal process ofthe precursor, the spacing and density of the hemispherical ZnO nanorods array could be adjusted easily. At the same time, the light-trapping effect in the visible region from450nm to640nm adjusted to480nm,650nm.2、The photoelectric properties of ZnO nanorod arrays were intensively investigated by varioustechniques. The efficiency of the dye-sensitized solar cell based on hemispherical was studied by soakingthe dye molecule N719. The result indicated that there were no obvious changes on different structures ofZnO nanorod arrays. The reason of the much lower efficiency of ZnO nanostructures may be the contactproperty between the FTO substrate and the ZnO nanorod arrays. In addition, the length of rods was soshort which would make the low adsorption of dye molecules on its surface. In order to improve the chargetransfer performance of ZnO nanorod arrays, a thin layer of gold was prepared on the surface of the PMMAand then magnetron sputtering zinc oxide seed layer and hydrothermally grown ZnO nanorod arrays. Thephotoelectric properties of this novel ZnO nanorod arrays were studied from the I-V characteristics. Theresult indicated that the dark current and photocurrent were all improved with increasing the precursorconcentration and growing time in the hydrothermal process.3、Taked into account the gold film would not only increased the charge transport properties, but alsofurther comprising a plasma resonance effect. The property of different sputtering time of gold layers wasstudied by UV-visible (UV-Vis) absorption spectroscopy. Two absorption peaks were observed from theabsorption spectra, one of which was the characteristic peak of the gold itself, its wavelength was at about590nm, another absorption peak between about880nm to890nm which was assigned to the surfaceplasma resonance (SPR) effect of gold nanostructures.