From Isotropic to Anisotropic Conductivities in P(NDI2OD-T2) by (Electro-)Chemical Doping Strategies

Abstract

Both electrochemical and chemical doping of the n-type regioregular polymer poly{[N,N′-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5′-(2,2′-bithiophene)} (P(NDI2OD-T2)) and its regioirregular counterparts are presented. Electrochemical doping clearly shows that a 2-fold reduction with maximum conductivity in the radical-anion state is possible with the polymers. Chemical doping with the state-of-the-art high-performance dopants 4-(2,3-dihydro-1,3-dimethyl-1H-benzimidazol-2-yl)-N,N-dimethylbenzeneamine (N-DMBI) and tetrakis(dimethylamino)ethylene (TDAE) gives conductivity values between 10–4 and 10–3 S cm–1 for as-cast films with clear involvement of the radical-anion species. Anisotropic conductivities of vapor-doped blade-coated films give up to 6 times higher values along the polymer chain direction compared with the perpendicular direction, both in face-on and edge-on oriented chains in the bulk of the films. The polymorph concomitantly changes from a mixed stacking of na...