Nanoscale phase separation control in rationally designed conjugated polymer solar cells processed using co-additives

A conjugated polymer based on benzo[1,2-b: 4,5-b'] dithiophene with a thiophene-conjugated side chain and N-alkylthieno[3,4-c] pyrrole-4,6-dione was synthesized. When shortening the alkyl to linear hexyl on thiophene, the polymer (PBDT2T6-TPD) still has good solubility in common solvents and the hole mobility is improved. By introducing two additives (1,8-diiodooctane and 1,6-dibromohexane) as co-additives in chlorobenzene solution, a nanoscale phase separation with excellent bicontinuous interpenetrating network and balanced hole mobility and electron mobility was obtained in the blend film of PBDT2T6-TPD and [6,6]-phenyl C61 butyric acid methyl ester. Combined with an appropriate side chain of polymer and post-processing of the device, the solar cells exhibit a power conversion efficiency of 6.73% with a remarkable short circuit current density of 12.91 mA cm(-2).