Mechanism of charge recombination and IPCE in ZnO dye-sensitized solar cells having I-/I3- and Br-/Br3- redox couple

The influence of intensity and wavelength variation on the solar cell parameters of two different ZnO-based liquid state DSSCs named as Cell (A) ZnO/EosinY/LiI and Cell (B) ZnO/EosinY/LiBr was studied. It was found that V-oc and I-sc depend logarithmically and linearly on light flux, respectively, which indicates that light absorption and carrier diffusion do not limit the solar cell efficiency. The data was analyzed to ascertain the charge recombination mechanism between conduction band electrons and the electrolytes. The regeneration of dye due to I-/I-3 and Br-/Br-3(-) redox couple was examined by studying the wavelength dependence of IPCE. An estimation of series and shunt resistance is made using two methods: (i) different illumination method (ii) single I-V curve, for the two cells in order to understand the role of the electrolyte in controlling the solar cell parameters. Copyright (C) 2010 John Wiley & Sons, Ltd.