A trilobal non-fullerene electron acceptor based on benzo[1,2-b:3,4-b′:5,6-b″] trithiophene and perylenediimide for polymer solar cells

Abstract

A trilobal non-fullerene electron acceptor, BTT-3PDI, incorporating benzo[1,2-b:3,4-b′:5,6-b″]trithiophene (BTT) as the core and three bay-substituted perylenediimides (PDIs) as the arms, was designed and synthetized. It shows a high electron mobility of 3.69×10−3cm2V−1s−1 because it is a crystalline semiconductor for the partially conjugated structure between PDI units and BTT core. BTT-3PDI shows a matched energy levels and a complementary absorption spectrum with PTB7-Th. The conventional polymer solar cells were fabricated without any processing additive or posttreatment. It showed a power conversion efficiency (PCE) of 1.35% because the unconspicuous microphase separation of the blend film leads to low electron mobility (1.67×10−5cm2V−1s−1) and hole mobility (2.80×10−5cm2V−1s−1). The study provides a proof that the crystalline PDI derivative with small dihedral angles between a core and PDI units can also avoid serious molecular aggregation and large phase separation in the active layer.