Impact of Morphology on Charge Carrier Transport and Thermoelectric Properties of N‐Type FBDOPV‐Based Polymers. (20th March 2020)

• Record Type: Journal Article
• Authors: 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
• Is Part Of: Advanced functional materials. Volume 30:Number 21(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-03-20
• Subjects: conjugated polymers -- molecular doping -- organic semiconductors -- thermoelectricity; Materials -- Periodicals; Chemical vapor deposition -- Periodicals; 620.11
• DOI: 10.1002/adfm.202000449
• Languages: English
• ISSNs: 1616-301X

Abstract

Abstract: 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‐C12 )). 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‐C12 ) (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‐C12 ) 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. Abstract : Two novel n‐type semiconducting FBDOPV‐based polymers are reported and studied in their neutral state and after doping with N‐DMBI. The relationships between morphology, charge carrier transport, and thermoelectric properties are unravelled and discussed. The best polymer shows a thermoelectric power factor of up to 0.72 µW m −1 K −2 and a figure of merit of 5.0 × 10 −4 at 388 K.