title: Thermal Gradient During Vacuum-Deposition Dramatically Enhances Charge Transport in Organic Semiconductors: Toward High-Performance N-Type Organic Field-Effect Transistors.
abstract: A thermal gradient distribution was applied to a substrate during the growth of a vacuum-deposited n-type organic semiconductor (OSC) film prepared from N,N'-bis(2-ethylhexyl)-1,7-dicyanoperylene-3,4:9,10-bis(dicarboxyimide) (PDI-CN2), and the electrical performances of the films deployed in organic field-effect transistors (OFETs) were characterized. The temperature gradient at the surface was controlled by tilting the substrate, which varied the temperature one-dimensionally between the heated bottom substrate and the cooled upper substrate. The vacuum-deposited OSC molecules diffused and rearranged on the surface according to the substrate temperature gradient, producing directional crystalline and grain structures in the PDI-CN2 film. The morphological and crystalline structures of the PDI-CN2 thin films grown under a vertical temperature gradient were dramatically enhanced, comparing with the structures obtained from either uniformly heated films or films prepared under a horizontally applied temperature gradient. The field effect mobilities of the PDI-CN2-FETs prepared using the vertically applied temperature gradient were as high as 0.59 cm2V-1s-1, more than a factor of 2 higher than the mobility of 0.25 cm2V-1s-1submitted to conventional thermal annealing and the mobility of 0.29 cm2V-1s-1from the horizontally applied temperature gradient.
authors.affiliation: Department of Physics, North Carolina State University , Raleigh, North Carolina 27695, United States.
authors.forename: Joo-Hyun
authors.initials: JH
authors.lastname: Kim
authors.affiliation: Department of Chemical and Biological Engineering, Hanbat National University , Daejeon 305-719, Korea.
authors.forename: Singu
authors.initials: S
authors.lastname: Han
authors.affiliation: Department of Chemical and Biological Engineering, Hanbat National University , Daejeon 305-719, Korea.
authors.forename: Heejeong
authors.initials: H
authors.lastname: Jeong
authors.affiliation: Department of Chemical and Biological Engineering, Hanbat National University , Daejeon 305-719, Korea.
authors.forename: Hayeong
authors.initials: H
authors.lastname: Jang
authors.affiliation: Department of Chemical and Biological Engineering, Hanbat National University , Daejeon 305-719, Korea.
authors.forename: Seolhee
authors.initials: S
authors.lastname: Baek
authors.affiliation: Department of Chemical and Biological Engineering, Hanbat National University , Daejeon 305-719, Korea.
authors.forename: Junbeom
authors.initials: J
authors.lastname: Hu
authors.affiliation: Department of Chemical and Biological Engineering, Hanbat National University , Daejeon 305-719, Korea.
authors.forename: Myungkyun
authors.initials: M
authors.lastname: Lee
authors.affiliation: Department of Chemical and Biological Engineering, Hanbat National University , Daejeon 305-719, Korea.
authors.forename: Byungwoo
authors.initials: B
authors.lastname: Choi
authors.affiliation: Department of Chemical and Biological Engineering, Hanbat National University , Daejeon 305-719, Korea.
authors.forename: Hwa Sung
authors.identifier: http://orcid.org/0000-0001-9131-810X
authors.initials: HS
authors.lastname: Lee
keywords: gradient thermal distribution; n-type organic semiconductor; organic field-effect transistor; thermal annealing; vacuum deposition