Multiple electron injection from dyes to titania layer for high efficiency-dye-sensitized solar cells

We report two kinds of dye-sensitized solar cells where multiple electron injection mechanism is used. One is multiple electron injection consisting of linearly linked two dye molecules. Tin(IV) 2,11,20,29-tetra-tert-butyl-2,3-naphthalocyanine (NcSn) was adsorbed on a SnO₂ surface by a Sn(p)-O-Sn(n) linkage, where Sn(p) and Sn(n) stand for a Sn atom on a Sn nanoparticle surface and that at the center of NcSn, respectively. Cis-diisothiocyanato - bis(2,2´-bipyridyl-4,4´-dicarboxylato) ruthenium(II) bis(tetrabutylammonium), known as N719, was bonded to NcSn by a-Sn(n)-O-CO-linkage. The incident photon to photocurrent efficiency (IPCE) curve of the cell (DD-cell) suggested that electrons are injected from both N719 and NcSn to SnO₂ nanoparticles. The mechanism was supported by transient absorption spectra studies. The other is multiple electron injection from double titania layer (top and bottom layers). The top and bottom electrodes were stained with different dyes having different λ max. A top layer fabricated on a glass was mechanically pressed with a bottom layer fabricated on a glass cloth to fabricate an anode. The glass cloth acts as a supporter of a porous titania layer as well as a holder of electrolyte. The incident photon to current efficiency (IPCE) curve had two peaks corresponding to those of the two dyes, which demonstrates that electrons are collected from both the top and bottom layers.