Determination of recombination mechanisms in organic solar cells

Studies of the recombination mechanisms in bulk heterojunction solar cells are reported. DC and transient photoconductivity are used to measure the carrier mobility and recombination times and also to show that geminate recombination is not significant in P3HT/PCBM and PCDTBT/PCBM cells. Light intensity measurements indicate that recombination is mostly monomolecular up to 1-sun light intensity. We conclude that the recombination at interface states within the bulk heterojunction structure is the dominant recombination mechanism.