title: Novel Effects of Compressed CO2Molecules on Structural Ordering and Charge Transport in Conjugated Poly(3-hexylthiophene) Thin Films.
abstract: We report the effects of compressed CO2molecules as a novel plasticization agent for poly(3-hexylthiophene) (P3HT)-conjugated polymer thin films. In situ neutron reflectivity experiments demonstrated the excess sorption of CO2molecules 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 proved that these CO2molecules accelerated the crystallization process of the polymer on the basis of ex situ grazing incidence X-ray diffraction measurements after drying the films via rapid depressurization to atmospheric pressure: both the out-of-plane lamellar ordering of the backbone chains and the intraplane π-π stacking of the side chains were significantly improved, when compared with 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 with 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 CO2annealing near the critical point can be useful as a robust processing strategy for improving the structural and electrical characteristics of other semiconducting conjugated polymers and related systems such as polymer:fullerene bulk heterojunction films.
authors.affiliation: Department of Materials Science and Chemical Engineering, Stony Brook University , Stony Brook, New York 11794-2275, United States.
authors.forename: Naisheng
authors.initials: N
authors.lastname: Jiang
authors.affiliation: Department of Materials Science and Chemical Engineering, Stony Brook University , Stony Brook, New York 11794-2275, United States.
authors.forename: Levent
authors.initials: L
authors.lastname: Sendogdular
authors.affiliation: Department of Materials Science and Chemical Engineering, Stony Brook University , Stony Brook, New York 11794-2275, United States.
authors.forename: Mani
authors.initials: M
authors.lastname: Sen
authors.affiliation: Department of Materials Science and Chemical Engineering, Stony Brook University , Stony Brook, New York 11794-2275, United States.
authors.forename: Maya K
authors.initials: MK
authors.lastname: Endoh
authors.affiliation: Department of Materials Science and Chemical Engineering, Stony Brook University , Stony Brook, New York 11794-2275, United States.|Department of Chemistry, Stony Brook University , Stony Brook, New York 11794-3400, United States.
authors.forename: Tadanori
authors.initials: T
authors.lastname: Koga
authors.affiliation: National Synchrotron Light Source II, Brookhaven National Laboratory , Upton, New York 11973, United States.
authors.forename: Masafumi
authors.initials: M
authors.lastname: Fukuto
authors.affiliation: Department of Chemistry, Bogazici University , Bebek, Istanbul 34342, Turkey.
authors.forename: Bulent
authors.initials: B
authors.lastname: Akgun
authors.affiliation: Center for Neutron Research, National Institute of Standards and Technology , Gaithersburg, Maryland 20899, United States.
authors.forename: Sushil K
authors.initials: SK
authors.lastname: Satija
authors.affiliation: Center for Functional Nanomaterials, Brookhaven National Laboratory , Upton, New York 11973-5000, United States.
authors.forename: Chang-Yong
authors.initials: CY
authors.lastname: Nam