title: Thermoelectric Enhancement by Compositing Carbon Nanotubes into Iodine-Doped Poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene].
abstract: Free-standing iodine-doped composite samples of poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) with carbon nanotubes (NTs) showed thermoelectric (TE) power factors (PFs) up to 33 μW·m-1·K-2after optimizing multiple factors, including: (1) sample fabrication solvent, (2) doping time, (3) average MEH-PPV molecular weight, (4) NT fraction in the composite, and (5) use of single-wall versus multi-wall nanotubes (SWNT and MWNT, respectively). Composite fabrication from halogenated solvents gave the best TE performance after iodine doping times of 2-4 h; performance drops substantially in ∼20 h doped samples. TE performance dropped after at least 24 h of removal from iodine vapor but was fully restored upon re-exposure to the dopant. Longer-chain MEH-PPV gave not only mechanically stronger films but also higher PFs in doped SWNT composites. MWNT composites gave low PFs, attributed to poor NT dispersion. Scanning electron microscopy showed increasingly extensive network formation as NT fraction increased in the composites; this phase separation provides charge transport pathways that improve thermoelectric PFs. The results support a strategy of producing phase-separated materials having both electrical conduction enhanced regions and Seebeck thermopower retaining regions to maximize organic TE response.
authors.affiliation: Department of Chemistry, University of Massachusetts , Amherst, Massachusetts 01003, United States.
authors.forename: Murat
authors.initials: M
authors.lastname: Tonga
authors.affiliation: Department of Chemistry, University of Massachusetts , Amherst, Massachusetts 01003, United States.
authors.forename: Lang
authors.initials: L
authors.lastname: Wei
authors.affiliation: Department of Polymer Science and Engineering, University of Massachusetts , Amherst, Massachusetts 01003, United States.
authors.forename: Patrick S
authors.initials: PS
authors.lastname: Taylor
authors.affiliation: Natick Soldier Research, Development and Engineering Center , Natick, Massachusetts 01760, United States.
authors.forename: Eugene
authors.initials: E
authors.lastname: Wilusz
authors.affiliation: Department of Polymer Science and Engineering, University of Massachusetts , Amherst, Massachusetts 01003, United States.
authors.forename: Ljiljana
authors.initials: L
authors.lastname: Korugic-Karasz
authors.affiliation: Department of Polymer Science and Engineering, University of Massachusetts , Amherst, Massachusetts 01003, United States.
authors.forename: Frank E
authors.initials: FE
authors.lastname: Karasz
authors.affiliation: Department of Chemistry, University of Massachusetts , Amherst, Massachusetts 01003, United States.
authors.forename: Paul M
authors.identifier: http://orcid.org/0000-0003-4255-4733
authors.initials: PM
authors.lastname: Lahti
keywords: MEH-PPV; doped polymer thermoelectrics; multi-wall carbon nanotubes; organic polymer thermoelectrics; polymer−nanotube composites; scanning electron microscopy; single-wall carbon nanotubes