Single Ether‐Based Side Chains in Conjugated Polymers: Toward Power Factors of 2.9 mW m−1 K−2

Abstract Combining side chain engineering and controlled alignment of PBTTT is an effective strategy to produce oriented thin films with improved thermoelectric performance when doped sequentially with the acceptor molecule hexafluoro‐tetracyanonaphthoquinodimethane (F 6 TCNNQ). The substitution of linear alkyl side‐chains ( n ‐C 12 ) with a chain of identical length including an ether function ( n ‐C 7 OC 4 ) leads to a new class of slightly polar PBTTT polymers, preserving the ease of synthesis and air stability of alkylated PBTTTs. This side‐chain modification improves the structural order of PBTTT backbones and the thermo‐mechanical properties of the polymer. It then can be oriented by high temperature rubbing up to 240 ° C to reach very high dichroic ratios up to 20 thanks to enhanced cohesive forces within side‐chain layers. The side chain polarity of n ‐C 7 OC 4 helps to tune the polymer‐dopant interactions. A multi‐technique approach demonstrates that F 6 TCNNQ dopants are randomly oriented in the disordered side chain layers of n ‐C 7 OC 4 with some evidence of dopant clustering. The combination of improved alignment and random orientation of intercalated F 6 TCNNQ dopants helps reach a very high charge conductivity σ = 5 ⋅ 10 4 S cm −1 and a record power factor of 2.9 mW m −1 K −2 in the polymer chain direction.