Toward High Performance n-Type Thermoelectric Materials by Rational Modification of BDPPV Backbones.

Three n-type polymers BDPPV, ClBDPPV, and FBDPPV which exhibit outstanding electrical conductivities when mixed with an n-type dopant, N-DMBI ((4-(1,3-dimethyl-2,3-dihydro-1H-benzoimidazol-2-yl)phenyl)dimethylamine), in solution. High electron mobility and an efficient doping process endow FBDPPV with the highest electrical conductivities of 14 S cm(-1) and power factors up to 28 μW m(-1) K(-2), which is the highest thermoelectric (TE) power factor that has been reported for solution processable n-type conjugated polymers. Our investigations reveal that introduction of halogen atoms to the polymer backbones has a dramatic influence on not only the electron mobilities but also the doping levels, both of which are critical to the electrical conductivities. This work suggests the significance of rational modification of polymer structures and opens the gate for applying the rapidly developed organic semiconductors with high carrier mobilities to thermoelectric field.