Depletion layer studies and carrier photogeneration in doped merocyanine photovoltaic cells

Abstract

The capacitance and photocurrent of Al/Cl2-doped merocyanine/Au thin film photovoltaic cells have been studied as a function of applied voltage bias. The capacitance data indicated that a Schottky barrier had formed between the Al and organic dye. The barrier width, built-in potential, and carrier concentration were 23 nm, 1.05 V, and 1018 cm−3, respectively. Photocurrent measurements at different excitation wavelengths strongly suggest that carrier photogeneration is a bulk phenomenon. Combining these observations with a study of the effects of doping with molecular chlorine, we propose that carriers are generated by electron transfer from a thermalized exciton to a dopant site. The dopant is thought to be adsorbed in the dye layer as the acceptor half of a weak charge transfer complex. A quantum yield of 11.2% at 632.8 nm based on light absorbed by a 30-nm thick merocyanine film was measured for the chlorine-doped cell.