Photovoltage bleaching in bulk heterojunction solar cells through population of the singlet exciton

摘要

The effect of illumination by a tunable light source on the open circuit voltage of a poly[2-methoxy-5-(3,7-dimethyloctyloxy)]-l,4-phenylenevinylene (MDMO-PPV): [6,6]-phenyl-C61 -butyric acid methyl ester (PCBM) bulk heterojunction solar cell is measured. Illumination at the energy of the PCBM ground state singlet exciton causes a sharp decrease in the photovoltage, while illumination at the MDMO-PPV exciton produces no change. Capacitive photocurrent spectroscopy reveals that the charge dissociated from the PCBM exciton is large despite the small photovoltage signal. This implies that polarons generated by the below gap excitation promote recombination of the above gap photoexcited charge.