A dye-sensitized solar cell using pheophytin–carotenoid adduct: Enhancement of photocurrent by electron and singlet-energy transfer and by suppression of singlet–triplet annihilation due to the presence of the carotenoid moiety

Titania-based solar cells were fabricated by the use of a pheophytin derivative and a pheophytin–carotenoid adduct. The addition of the carotenoid moiety increased the photocurrent (Jsc = 3.7 → 6.0 mA cm−2), reduced the photovoltage (Voc = 0.53 → 0.46 V), and enhanced the solar energy-to-electricity conversion efficiency (η = 1.4 → 1.8%). The increase in photocurrent was explained in terms of electron and singlet-energy transfer from the carotenoid to the chlorin moiety as well as the prevention of the chlorin aggregate by the bulky carotenoid moiety and the resultant suppression of the singlet–triplet annihilation reaction.