Selective Doping of Conjugated Block Copolymer for Organic Thermoelectric Applications

ABSTRACT We demonstrate the selectively p- or n-type doping behavior of conjugated block copolymer (BCP). The poly(3-hexylthiophene)-b-poly{[N,N-9-bis(2-octyldodecyl)-naphtalene-1, 4, 5, 7-bis(dicarboximide)-2,6-diyl]-alt-5,59-(2,29-bithiophene)}, P3HT-b-P(NDI2OD-T2), has been successfully synthesized via Stille-coupling polymerization, and these p- and n-type blocks containing BCP can be doped using either F4TCNQ or N-DMBI, generating holes or electrons as carriers, respectively. The electrical conductivity of p-doped BCP is 1.4 × 10−3 S·cm−1, whereas, for n-doped BCP, the film conductivity is 1.7 × 10−4 S·cm−1 using the four-probe method. Further, we investigate the Seebeck coefficient of doped BCP, evaluating the potential properties for thermoelectric applications. The analysis results show that the synthesized conjugated BCP can be doped either way to induce holes or electrons from a single composite polymer, and when one block is doped, the other un-doped block has no influence on the electrical conductivity. Accordingly, doping either the p- or n-type phenomenon of a single polymer is demonstrated in this study, realizing a new strategy not only for thermoelectric materials but also for overall organic electric applications.