Effect of traps on the performance of bulk heterojunction organic solar cells

The effect of electron traps on the performance of bulk heterojunction organic solar cells made of poly[2-methoxy-5-(3('),7(')-dimethyloctyloxy)-1,4-phenylene vinylene] blended with [6,6]-phenyl-C(61)-butyric acid methyl ester (PCBM) is investigated. By deliberately introducing 7,7,8,8-tetracyanoquinodimethane, which is a stronger electron accepting molecule than PCBM, the electron transport in the solar cells becomes trap limited. We demonstrate that the open circuit voltage and its light-intensity dependence are strongly affected by recombination of holes with trapped electrons. Depending on the amount of traps, their recombination strength, and the light intensity, the losses due to trap-assisted recombination can even dominate over the intrinsic bimolecular recombination. (c) 2007 American Institute of Physics