Enhancing electron collection efficiency and effective diffusion length in dye-sensitized solar cells

Intensity-modulated photocurrent spectroscopy and intensitymodulated photovoltage spectroscopy are employed to measure the dynamics of electron transport and recombination in the ZnO nanowire (NW) array-ZnO/layered basic zinc acetate (LBZA) nanoparticle (NP) composite dye-sensitized solar cells (DSSCs). The roles of the vertical ZnO NWs and insulating LBZA in the electron collection and transport in DSSCs are investigated by comparing the results to those in the TiO₂ - NP, horizontal TiO₂ - NW and vertical ZnO-NW-array DSSCs. The electron trans-port rate and electron lifetime in the ZnO NW/NP composite DSSC are superior to those in the conventional TiO ₂-NP cell due to the existence of the vertical ZnO NWs and insulating LBZA. It indicates that the ZnO NW/NP composite anode is able to sustain efficient electron collection over much greater thickness than the TiO ₂-NP cell does. Consequently, a larger effective electron diffusion length is available in the ZnO composite DSSC.