High performance Langmuir-Schaeffer film transistors based on air stable n-type diperylene bisimide

Diperylene Bisimide (DIPP-diPBI) mono- and/or multi-layer film using Langmuir-Schaeffer (LS) techniques has been fabricated and the OFET device performance based on the as-prepared LS film is investigated. The thickness of monolayer film is determined to be 2.3 nm by using atomic force microscopy, which is closely matched with the interplanar spacing estimated from the XRD spectra. The length of molecular long axis is measured to be 21.9 angstrom from the DFT optimized configuration, indicating that the long axis of molecule in LS film approximately stands upright on hydrophobic substrates. The absorption maximum at 417 nm shows a good linear corrleation with the layer number, proving the obtained films are deposited in a layer-by-layer fassion. The film with precision control of the long-range order and lateral packing density by LS deposition exhibits good electron injection properties and high FET device performance. The charge transport behavior is also investigated as a function of the layer number of LS film. The electron mobility gradually increases with the number of layers and saturates at a plateau with a mean value of 0.03 cm(2) V (1) s (1) in the atmosphere upon completion of the first eight layers. It is a direct evidence of physical size of charge transport layer. Furthermore, the fabricated FET device exhibits long-time stability in the air. The integration of LS method with air stability of the n-type compound affords an opportunity to explore solution-phase self-assembly and electronic devices fabrication with controllable molecular layers. (C) 2013 Elsevier B. V. All rights reserved.