Fabrication of ZnO films consisting of densely accumulated mesoporous nanosheets and their dye-sensitized solar cell performance

Nanocrystalline and mesoporous ZnO films approximately 4 mu m in thickness were fabricated through a simple chemical deposition of Zn4CO3 (OH)(6)center dot H2O in an aqueous solution of zinc nitrate and urea and subsequent pyrolysis at a low temperature of 300C. Microscopic observation of the films revealed that they were composed of mesoporous nanosheets accumulating with submicrometer-order spacing between them on conductin(2 glass substrates. Adsorption of N-719 dye onto the ZnO surface, for application to dye-sensitized solar cells, led to dye-loading of 1.1 x 10(-7) mol/cm(2) in spite of the relatively small thickness. The resultant ZnO/N-719 photoanode exhibited a short-circuit photocurrent density of 13.8 mA/cm(2). which is of the highest level ever reported for ZnO. An overall light-to-electricity conversion efficiency of 3.3% was achieved under I sun AM1.5 illumination without any optimization in view of the other cell components. (c) 2007 Elsevier B.V All rights reserved.