Novel Effects of Compressed CO₂ Molecules on Structural Ordering and Charge Transport in Conjugated Poly(3-hexylthiophene) Thin Films

Journal Article · Thu Oct 06 00:00:00 EDT 2016 · Langmuir

DOI:https://doi.org/10.1021/acs.langmuir.6b03239· OSTI ID:1341638

Jiang, Naisheng ^[1]; Sendogdular, Levent ^[1]; Sen, Mani ^[1]; Endoh, Maya K. ^[1]; Koga, Tadanori ^[1]; Fukuto, Masafumi ^[2]; Akgun, Bulent ^[3]; Satija, Sushil K. ^[4]; Nam, Chang-Yong ^[5]

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1. Stony Brook Univ., NY (United States)
2. Brookhaven National Lab. (BNL), Upton, NY (United States)
3. Bogazici Univ. (Turkey)
4. National Inst. of Standards and Technology (NIST), Gaithersburg, MD (United States)
5. Brookhaven National Lab. (BNL), Upton, NY (United States). Center for Functional Nanomaterials (CFN)

We report the effects of compressed CO₂ molecules as a novel plasticization agent for poly(3- hexylthiophene) (P3HT) conjugated polymer thin films. In-situ neutron reflectivity experiment demonstrated the excess sorption of CO₂ molecules in the P3HT thin films (about 40 nm in thickness) at low pressure (P = 8.2 MPa) under the isothermal condition of T = 36 °C, which is far below the polymer bulk melting point. The results evidenced that these CO₂ molecules accelerated the crystallization process of the polymer on the basis of ex-situ grazing incidence Xray diffraction measurements after drying the films via rapid depressurization to atmospheric pressure: not only the out-of-plane lamellar ordering of the backbone chains but also intra-plane π-π stacking of the side chains were significantly improved, when compared to those in the control P3HT films subjected to conventional thermal annealing (at T = 170 °C). Electrical measurements elucidated that the CO₂-annealed P3HT thin films exhibited enhanced charge carrier mobility along with decreased background charge carrier concentration and trap density compared to those in the thermally annealed counterpart. This is attributed to the CO₂-induced increase in polymer chain mobility that can drive the detrapping of molecular oxygen and healing of conformational defects in the polymer thin film. Given the universality of the excess sorption of CO₂regardless of the type of polymers, the present findings suggest that the CO₂ annealing near the critical point can be useful as a robust processing strategy for improving structural and electrical characteristics of other semiconducting conjugated polymers and related systems such as polymer: fullerene bulk heterojunction films.tion films.

• Research Organization: Brookhaven National Lab. (BNL), Upton, NY (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES)
• Grant/Contract Number: SC00112704
• OSTI ID: 1341638
• Report Number(s): BNL-113348-2016-JA; TRN: US1701566
• Journal Information: Langmuir, Vol. 32, Issue 42; ISSN 0743-7463
• Publisher: American Chemical Society
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE