Quasi-solid-state Dye-sensitized Solar Cells with Macropore-containing Hierarchical Electrodes

We investigated the influence of macropores in TiO2 electrodes on photovoltaic properties of quasi-solid-state dye-sensitized solar cells. We constructed a macropore-incorporated mesopore photoelectrode and compared the photovoltaic properties of this electrode with those of conventional electrodes containing only mesopores in the presence of a quasi-solid-state PGE. The polymer gel electrolyte (PGE) was prepared based on poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) with TiO2 nanoparticle fillers. The quasi-solid-state DSCs comprising the macropore-containing electrode displayed a photon-to-electron conversion efficiency comparable to that obtained using liquid electrolyte DSCs (90% of the efficiency of the liquid electrolyte DSCs), whereas the mesopore electrode displayed only 80% of the efficiency. Long-term stability measurements showed that the macropore-containing electrode maintained its efficiency during the period of thermal aging, whereas the mesopores electrode showed a significant decrease in the photocurrent density and, therefore, the efficiency. Notably, a direct observation of PGE infiltration by using a model particle revealed an incomplete infiltration of nanofillers into the mesopore. An impedance analysis confirmed that the incomplete infiltration increased the recombination rate at the electrode/electrolyte interface and therefore decreased the photocurrent density. (C) 2014 Elsevier Ltd. All rights reserved.