Manipulating backbone structure with various conjugated spacers to enhance photovoltaic performance of D-A-type two-dimensional copolymers

A class of two-dimensional low band-gap polymers containing thiophene- substituted benzo[1,2-b:4,5-b′]-dithiophene (BDTT) and fluorinated quinoxaline (Q) units were synthesized with varied conjugated spacers. Significant effect of the spacers on the photo-physical and photovoltaic properties was exhibited. Holes mobility up to 0.22 × 10−3 cm2 V−1 s−1 was achieved for the polymer PBDTT-BTQ bearing bithiophene unit in the backbone and the PBDTT-TQ-based PSCs exhibited the best performance with a PCE up to 5.9%.125