A dye-sensitized solar cell based on a boron-doped ZnO (BZO) film with double light-scattering-layers structured photoanode

A double light-scattering-layer boron-doped ZnO (DL-BZO) film based dye-sensitized solar cell (DSSC) is fabricated with a high energy conversion efficiency of 7.2%. The over layer is made of well dispersed sub-micrometer-sized boron-doped ZnO (BZO) sphere arrays (SSA-BZO) to facilitate the fastest movement of electrons towards the electrodes and also function as light scattering centers. The under-layer, consisting of a nanoporous BZO nanoparticulate (NP-BZO) film, increases the dye adsorption and also reduces the injected electrons recombination. The DL-BZO film boosted the cell efficiencies because of its improved light-harvesting ability, larger surface area, photon-to-electron mechanism and doping of the ZnO films. The efficiency of 7.2% achieved for DL-BZO is much larger than the 4.1% obtained for double light-scattering-layers for undoped ZnO (DL-ZnO) films and is also higher than the 2.1% achieved for monolayer NP-BZO films. Addition of an SSA-BZO layer over the NP-BZO layer significantly improves the transport of electrons and their lifetime when compared to the NP-BZO film only. The DL-BZO film exhibit the slowest recombination rate of changes compared with the other films and is found to be a major factor for the improved cell efficiency. The cells exhibit high stability, in terms of cell performance, even after 35 days. The highest efficiency achieved in the present study is the highest ever reported for a double light-scattering-layer ZnO film-based DSSC.