Novel ZnO-Based Film with Double Light-Scattering Layers as Photoelectrodes for Enhanced Efficiency in Dye-Sensitized Solar Cells

A novel double light-scattering-layer ZnO (DL-ZnO) film consisting of ZnO monodisperse aggregates (MA-ZnO) as underlayer and sub-micrometer-sized platelike ZnO (SP-ZnO) as overlayer was fabricated and studied as dye-sensitized solar-cell photoanodes. It was found that DL-ZnO could significantly improve the efficiency of dye-sensitized solar cells (DSSCs) owing to its relatively high surface area and enhanced light-scattering capability. The overall energy-conversion efficiency (eta) of 3.44% was achieved by the formation of DL-ZnO film, which is 47% higher than that formed by MA-ZnO alone and far larger than that formed by SP-ZnO alone (eta = 0.81%). Furthermore, the eta decay measurements for DL-ZnO cell showed that no significant decrease of eta occurred even when DL-ZnO cell was placed for 100 h at ambient temperature. The charge recombination behavior of cells was investigated by electrochemical impedance spectra (EIS), and the results showed that among MA-ZnO, SP-ZnO, and DL-ZnO based cells, DL-ZnO based cell with double scattering layers has the lowest transfer resistance and the longest electron lifetime, which Could facilitate the reduction of recombination processes and thus Would promote the solar-cell performance.