Probing charge delocalization in a semi-crystalline supramolecular polymer

Various doping methods have achieved metallic conductivity in $\pi$-conjugated polymer but most of them suffer from dopant-induced-disorder. We developed a simple and effective method of doping a high mobility semi-crystalline polymer, poly(2,5-bis(3-hexadecylthiophen-2-yl)thieno[3,2-b]thiophene) (pBTTT) by forming a bi-layer with a small-molecule acceptor, 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F$_{4}$-TCNQ). The doping realizes an efficient charge-transfer between pBTTT and F$_{4}$-TCNQ (conductivity over 150 S/cm), while preserving the structural order of a pristine pBTTT. The charges are discovered to be sufficiently delocalized to give rise to a nearly-ideal Hall effect, and therefore, a coherent transport in a wide temperature range, with a high Hall mobility of 1.8 cm$^{2}$/Vs at room temperature. The combination of a Pauli magnetic susceptibility and magnetoconductance signatures strengthen the evidence of weak localization in the supramolecular system. Comparison with other amorphous conducting polymers elucidates the role of structural order as an indicator of the degree of charge delocalization.