Slow electron injection on Ru-phthalocyanine sensitized TiO2

Photoinduced electron injection in dye sensitized TiO2 is a critical step in the function of dye sensitized solar cells. High electron injection quantum yields are a requirement to obtain efficient devices. While high electron injection quantum yields are usually linked to ultrafast electron-transfer dynamics (in the fs-ps timescales), the latter are not a requirement. We present here a system, Ru-phthalocyanine sensitized TiO2, where slow electron injection (k (inj) approximate to 450 ns(-1)) and efficient electron injection are compatible owing to the long lifetime of the injecting state, the Ru-phthalocyanine triplet state. Ru-phthalocyanine dyes are attractive sensitizers because they absorb strongly in the red and their axial ligands hinder the formation of aggregates.