Slow Electron Injection on Ru−Phthalocyanine Sensitized TiO₂

Abstract

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 (<i>k</i>_inj ≈ 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.