Backbone Structure Effect on the Thermoelectric Properties of IDT‐Based p‐Type Conjugated Polymers

Abstract

Four conjugated polymers are synthesized through indacenodithiohene (IDT) unit copolymerized with thiophene and thiophene derivatives. Indacenodithiohene‐co‐thieno[3,2‐b]thiophene (IDT‐TT) and indacenodithiohene‐co‐trans‐1,2‐di(2‐thienyl)ethylene (IDT‐TVT) exhibit better charge transport mobilities than indacenodithiohene‐co‐thiophene (IDT‐T) and indacenodithiohene‐co‐3,4‐ethoxylene dioxythiophene (IDT‐EDOT), and also display superior thermoelectric properties after doping. Theoretical calculations suggest that IDT‐EDOT and IDT‐TVT have better coplanarities; the inferior performance for IDT‐EDOT might be due to its low molecular weight. Meanwhile, it is worth mentioning that via the synergistic effect of two dopants (CN6CP, CuTFSI), the electrical conductivities of the polymers are further improved. The XPS data shows that the coordination interaction between copper ion and the cyano groups of CN6CP introduces cupric ions into the polymer films, which leads to the increase of the doping ratio.

Correlation of Thermoelectric Performance, Domain Morphology and Doping Level in PEDOT:PSS Thin Films Post‐Treated with Ionic Liquids

“…[ 8–10 ] Commonly used conductive polymers are usually based on a conjugated backbone structure, like in polyacetylene, polypyrrole, polyaniline, or polythiophene. [ 11 ] With different techniques of doping, [ 12–14 ] side chain variations, [ 14 ] or backbone modifications [ 15 ] the thermoelectric performance can be positively influenced.…”

Structure and Doping Optimization of IDT-Based Copolymers for Thermoelectrics

“…Herein, we selected the indacenodithiophene (IDT) building block as the OTE material since the IDT skeleton has two thiophene rings attached with a central benzene ring that provide strong intermolecular interactions with ordered packing [ 26 , 27 , 28 ], which is beneficial for improving the electrical conductivity of OTE materials. IDT-based polymers have been widely used in organic field effect transistor (OFET) and solar cell applications [ 29 , 30 , 31 ]; however, although research on its TE properties has also been reported [ 32 , 33 ], the TE performance is still very low, and the detailed structure–property relationships are not comprehensive. In addition, we have recently reported IDT-based composite thermoelectric materials and found that the composites showed good performance with power factor of 161.34 mW/m −1 K 2 [ 34 ].…”

Enhanced Thermoelectric Performance of Indacenodithiophene-Benzothiadiazole Copolymer Containing Polar Side Chains and Single Wall Carbon Nanotubes Composites

“…[8][9][10][11][12] due to their low toxicity, low thermal conductivity and mechanical flexibility. Recent results have shown that CPs are among the most promising materials for application in flexible thermoelectric generators [13][14][15][16][17]. For example, poly(3,4-ethylenedioxy-thiophene) (PEDOT) with a high thermoelectric figure of merit (ZT) of 0.45 has been reported [18], which stimulated the investigation of CPs to be used for thermoelectric generators.…”

“…Organic materials generally possess large Seebeck coefficients (S) and low thermal conductivity [13][14][15][16][17][18][19], therefore, the main challenge of achieving high-performance OTEs is how to improve the electrical conductivity of CPs without sacrificing their large Seebeck coefficients and low thermal conductivity [20,21]. Many strategies have been attempted to improve the conductivities of CPs (such as structural manipulations [22], strengthening the ordering of polymer packing [23], efficient doping [24], and forming composites with highly conductive inorganic materials [25], etc.…”