Polymer solar cells employing conjugated polyelectrolytes with different countercations

Conjugated polyelectrolytes based on benzotriazole (BT) and benzothiadiazole (BTz) alt unit with a pendant sulfonate ion but different countercations were synthesized and named PBTBTz-SO3Na and PBTBTz-SO3TBA. PBTBTz-SO3Na was used as a cathode interface applied to polymer solar cells (PSCs), and ITO/PEDOT:PSS/active layer/cathode interlayer/Al was set as a device structure. The PSCs displayed an average power conversion efficiency (PCE) of 7.7%, revealing an unchanged efficiency in comparison with that of the control device fabricated from a CH3OH interlayer. TBA+, a different counteraction, was used instead of Na+ to further study the influence of counterions on the electrical property of PBTBTz-SO3−. PBTBTz-SO3TBA was used as a cathode interface to fabricate two types of PSCs based on PTB7:PC71BM and PBDB-T:ITIC, and their improved average PCEs were 8.6% and 9.1%, respectively.