Effects of n-type perylene derivative as an additive on the power conversion efficiencies of polymer solar cells

The synthesized n-type perylene derivative, N, N′-bis-(5-bromopyridine-2-yl)-1,6,7,12-tetrakis(4-n-butoxyphenoxy)-3,4,9,10-perylene tetracarboxydiimide (PPyB), was applied to polymer solar cells as an additive in P3HT [poly(3-hexylthiophene)]:PCBM [[6,6]-phenyl C 61-butyric acid methyl ester] blend films. The addition of 1 wt% PPyB into a P3HT:PCBM layer led to a considerable improvement of over 70% in power conversion efficiency due to the enhanced short circuit current when compared with that of reference cell without an additive. Photoluminescence, X-ray measurements and carrier mobility studies revealed that the perylene additives increased electron mobility and contributed to more effective exciton dissociation due to the presence of the additive, PPyB, in the interfaces between the P3HT and PCBM domains.