Aspect-Ratio Dependent Electron Transport and Recombination in Dye-Sensitized Solar Cells fabricated with one-dimensional ZnO nanostructures

Abstract

Though one-dimensional (1-D) ZnO nanrods are promising transport electron transport material in the photoanode of Dye Sensitized Solar Cells (DSSC), 1-D ZnO nanorod based DSSCs exhibit poor energy conversion efficiencies. In this study, DSSCs were fabricated with 1-D ZnO nanorods having different aspect ratio and the dependence of solar cell performance on aspect ratio of ZnO nanorods was investigated. Photoanodes fabricated with different 1-D ZnO nanorods having aspect ratios of 4.4, 5.4, 5.8, 6.8 and 7.6 showed increasing solar cell performance with the increase of aspect ratio where 2.1 and 4.7% light conversion efficiencies were observed respectively for the lowest and highest aspect ratio of 1-D ZnO nanostructures. We study the electrical and operational differences between DSSC made with ZnO nanostructures with different aspect ratio. Electrochemical impedance spectroscopy (EIS) is used to quantify the aspect ratio depended electron transport properties, charge recombination, life-time and charge diffusion lengths of excited electrons in 1D ZnO nanorods and electron transport properties are correlated to the observed cell performance. In addition, effect of aspect ratio of ZnO nanorods on dye loading amount and light scattering properties were also investigated.