Field-Independent Charge Photogeneration in PCPDTBT/PC70BM Solar Cells

Transient absorption spectroscopy has been used to investigate charge photogeneration in organic solar cells based upon PCPDTBT/PC70BM (poly-[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b']-dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)]/[6,6]-phenyl-C-71-butyric acid methyl ester) photoactive layers as a function of externally applied bias. We find that the yield of dissociated polarons is independent of applied bias in these devices.