Effects of Arylene Diimide Thin Film Growth Conditions on n-Channel OFET Performance

✍ Scribed by Brooks A. Jones; Antonio Facchetti; Michael R. Wasielewski; Tobin J. Marks

• Publisher: John Wiley and Sons
• Year: 2008
• Tongue: English
• Weight: 486 KB
• Volume: 18
• Category: Article
• ISSN: 1616-301X
• DOI: 10.1002/adfm.200701045

✦ Synopsis

Abstract

A series of eight perylene diimide (PDI)‐ and naphthalene diimide (NDI)‐based organic semiconductors was used to fabricate organic field‐effect transistors (OFETs) on bare SiO~2~ substrates, with the substrate temperature during film deposition (T~d~) varied from 70–130 °C. For the N,N′‐n‐octyl materials that form highly ordered films, the mobility (µ) and current on‐off ratio (I~on~/I~off~) increase slightly from 70 to 90 °C, and remain relatively constant between 90 and 130 °C. I~on~/I~off~ and µ of dibromo‐PDI‐based OFETs decrease with increasing T~d~, while films of N,N′‐1__H__,1__H__‐perfluorobutyl dicyanoperylenediimide (PDI‐FCN~2~) exhibit dramatic I~on~/I~off~ and µ enhancements with increasing T~d~. Increased OFET mobility can be correlated with higher levels of molecular ordering and minimization of film morphology surface irregularities. Additionally, the effects of SiO~2~ surface modification with trimethylsilyl and octadecyltrichlorosilyl monolayers, as well as with polystyrene, are investigated for N,N′‐n‐octyl dicyanoperylenediimide (PDI‐8CN~2~) and PDI‐FCN~2~ films deposited at T~d~ = 130 °C. The SiO~2~ surface treatments have modest effects on PDI‐8CN~2~ OFET mobilities, but modulate the mobility and morphology of PDI‐FCN~2~ films substantially. Most importantly, the surface treatments result in substantially increased V~th~ and decreased I~off~ values for the dicyanoperylenediimide films relative to those grown on SiO~2~, resulting in V~th~ > 0.0 V and I~on~/I~off~ ratios as high as 10^8^. Enhancements in current modulation for these high‐mobility, air‐stable, and solution‐processable n‐type semiconductors, should prove useful in noise‐margin enhancement and further improvements in organic electronics.