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Impact of Morphology on Charge Carrier Transport and Thermoelectric Properties of N‐Type FBDOPV‐Based Polymers
Author(s) -
Bardagot Olivier,
Kubik Paweł,
Marszalek Tomasz,
Veyre Pawel,
Medjahed Asma Aicha,
Sandroni Martina,
Grévin Benjamin,
Pouget Stéphanie,
Nunes Domschke Tamara,
Carella Alexandre,
Gambarelli Serge,
Pisula Wojciech,
Demadrille Renaud
Publication year - 2020
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.202000449
Subject(s) - materials science , seebeck coefficient , thermoelectric effect , fluorene , doping , amorphous solid , acceptor , charge carrier , polymer , electron mobility , polaron , analytical chemistry (journal) , electron , thermal conductivity , crystallography , condensed matter physics , organic chemistry , thermodynamics , optoelectronics , chemistry , physics , composite material , quantum mechanics
The impact of the chemical structure and molecular order on the charge transport properties of two donor–acceptor copolymers in their neutral and doped states is investigated. Both polymers comprise 3,7‐bis((E)‐7‐fluoro‐1‐(2‐octyl‐dodecyl)‐2‐oxoindolin‐3‐ylidene)‐3,7‐dihydrobenzo[1,2‐ b :4,5‐ b ′]difuran‐2,6‐dione (FBDOPV) as electron‐accepting unit, copolymerized with 9,9‐dioctyl‐fluorene (P(FBDOPV‐F)) or with 3‐dodecyl‐2,2′‐bithiophene (P(FBDOPV‐2T‐C 12 )). These copolymers possess an amorphous and semi‐crystalline nature, respectively, and exhibit remarkable electron mobilities of 0.065 and 0.25 cm 2 V –1 s –1 in field effect transistors. However, after chemical n‐doping with 4‐(1,3‐dimethyl‐2,3‐dihydro‐1 H ‐benzoimidazol‐2‐yl)phenyl)dimethylamine (N‐DMBI), electrical conductivities four orders of magnitude higher can be achieved for P(FBDOPV‐2T‐C 12 ) (σ = 0.042 S cm −1 ). More charge‐transfer complexes are formed between P(FBDOPV‐F) and N‐DMBI, but the highly localized polaronic states poorly contribute to the charge transport. Doped P(FBDOPV‐2T‐C 12 ) exhibits a negative Seebeck coefficient of –265 µV K −1 and a thermoelectric power factor (PF) of 0.30 µW m −1 K −2 at 303 K which increases to 0.72 µW m −1 K −2 at 388 K. The in‐plane thermal conductivity (κ || = 0.53 W m −1 K −1 ) on the same micrometer‐thick solution‐processed film is measured, resulting in a figure of merit (ZT) of 5.0 × 10 −4 at 388 K. The results provide important design guidelines to improve the doping efficiency and thermoelectric properties of n‐type organic semiconductors.