engleski

Study of nanostructured zinc oxide thin films for organic photovoltaics by GISAXS/GIWAXS

Dye-sensitized solar cells (DSSC) have been regarded as potential candidates for next- generation solar cells due to their low cost, high durability, large flexibility in shape, and transparency. The most important part of typical DSSC is porous-structured transparent oxide film with adsorbed dye molecules as photosensitized anode. Currently, the primary photovoltaic material used as photosensitized anode is titanium dioxide (TiO 2 ), for which the considerable power conversion efficiency has been successfully accomplished. Besides TiO 2 , zinc oxide (ZnO) is also investigated as another promising candidate for anode materials because the band gap energy and conduction band edge of ZnO are similar to those of TiO 2 . Additionally, ZnO shows an order of magnitude higher electron mobility and the corresponding electron diffusion coefficient but conversion efficiency of DSSC based on ZnO is rather low in comparison to TiO 2 . The DSSC conversion efficiency can be improved by optimizing bulk and surface structure of ZnO layer (crystal structure, level of defects, surface roughness, porosity, pore size distribution). In this work ZnO:Al layers were prepared by magnetron sputtering and annealed at various temperatures. The structure of as deposited and annealed films was measured by XRD while estimation of defects level was done upon luminescence, optical, electrical and vibrational properties. The surface morphology was modified in two ways. One was electrochemical etching of as deposited films. In other type of experiments, thin film was modified by deposition of ZnO nanocrystals on the surface by spin coating technique. For this purpose, nanocrystals of proper size and size distribution were obtained by sol-gel process. In the next step ZnO samples with modified surface were sensitized by organic dye. The initial and final structures were investigated by using simultaneous Grazing Incidence Small and Wide Angle X-ray Scattering (GISAXS/GIWAXS).

zinc oxide thin films ; GISAXS/GIWAXS ; dye-sensitized solar cells

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