Effects of Potential Shift and Efficiency of Charge Collection on Nanotube-based Porphyrin-sensitized Solar Cells with Conjugated Links of Varied Length

For dye-sensitized solar-cell devices fabricated from porphyrin sensitizers with links of varied length (PE1-PE4) adsorbed on anodic titanium-oxide nanotube arrays, we measured induced photocurrent and photovoltage decays under constant bias illumination; the evaluated efficiencies of charge collection of the devices show a systematic trend PE4 > PE3 > PE2 > PE1 at a large short-circuit current, implying that a long link would improve the charge separation if the electrons were effectively injected into the semiconductor.