Enhanced n-Doping Efficiency of a Naphthalenediimide-Based Copolymer through Polar Side Chains for Organic Thermoelectrics
Anton Koster, L. Jan
KAUST DepartmentPhysical Sciences and Engineering (PSE) Division
Chemical Science Program
KAUST Solar Center (KSC)
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AbstractN-doping of conjugated polymers either requires a high dopant fraction or yields a low electrical conductivity because of their poor compatibility with molecular dopants. We explore n-doping of the polar naphthalenediimide–bithiophene copolymer p(gNDI-gT2) that carries oligoethylene glycol-based side chains and show that the polymer displays superior miscibility with the benzimidazole–dimethylbenzenamine-based n-dopant N-DMBI. The good compatibility of p(gNDI-gT2) and N-DMBI results in a relatively high doping efficiency of 13% for n-dopants, which leads to a high electrical conductivity of more than 10–1 S cm–1 for a dopant concentration of only 10 mol % when measured in an inert atmosphere. We find that the doped polymer is able to maintain its electrical conductivity for about 20 min when exposed to air and recovers rapidly when returned to a nitrogen atmosphere. Overall, solution coprocessing of p(gNDI-gT2) and N-DMBI results in a larger thermoelectric power factor of up to 0.4 μW K–2 m–1 compared to other NDI-based polymers.
CitationKiefer D, Giovannitti A, Sun H, Biskup T, Hofmann A, et al. (2018) Enhanced n-Doping Efficiency of a Naphthalenediimide-Based Copolymer through Polar Side Chains for Organic Thermoelectrics. ACS Energy Letters: 278–285. Available: http://dx.doi.org/10.1021/acsenergylett.7b01146.
SponsorsWe gratefully acknowledge financial support from the Swedish Research Council through Grant No. 2016-06146, the Knut and Alice Wallenberg Foundation through a Wallenberg Academy Fellowship, and the European Research Council (ERC) under Grant Agreement No. 637624. S.F. gratefully acknowledges support from VINNOVA (2015-04859) and the Swedish Research Council (2016-03979). Portions of this research were carried out at the Stanford Synchrotron Radiation Lightsource, a national user facility operated by Stanford University on behalf of the U.S. Department of Energy, Office of Basic Energy Sciences.
PublisherAmerican Chemical Society (ACS)
JournalACS Energy Letters