Quantifying Bimolecular Recombination Losses in Organic Bulk Heterojunction Solar Cells

We present a new experimental technique that affords direct quantification of the fraction of charge carriers lost in poly(3-hexylthiophene): fullerene solar cells by bimolecular recombination. Depending on annealing conditions up to 17% of carriers recombine bimolecularly under solar illumination. We explain our findings with a closed analytical expression for the photocurrent generated by an organic solar cell.