N-channel organic thin-film transistors based on a soluble cyclized perylene tetracarboxylic diimide dimer

A high soluble dimeric perylene tetracarboxylic diimide (1) was fabricated into the thin solid films by means of quasi-Langmuir-Shafer (QLS) method. The structure and properties of the QLS films were comparatively studied with those of monomeric perylene tetracarboxylic diimide (2) by electronic absorption, fluorescence, polarized electronic absorption spectroscopy, X-ray diffraction (XRD) and atomic force microscopy (AFM). Experimental results revealed the film crystallinity and general molecular order in the film of 1 are improved effectively in comparison with those of 2 due to the dimeric structure of 1. Electron mobilities as high as 0.03 cm(2) V-1 s(-1) for the films of novel dimeric 1 are achieved, which is much better than that of monomeric 2 (5.0 x 10(-7) cm(2) V-1 s(-1)). In particular, the electronic mobility of 1 only slightly decreased after exposure to air and remained almost unchanged after 90 days, which is attributed to molecular packing effects including close stacking of dimeric PDI units and segregation effects imparted by the 2-N, N-di(n-butyl) amino-4,6-dihydrazine-1,3,5-trazine unites as well as relatively low-lying LUMO energy level. The present result represents not only the first example of solution-processed, air-stable dimeric PDI-based n-type OFET, but more importantly provides an efficient way to enhance the performance of air-stable n-channel organic semiconductors through intramolecular bonding to pre-organizing the pi-conjugated organic molecules into a rigid cofacially stacked structure. (C) 2013 Elsevier B.V. All rights reserved.