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Cover Picture: n‐Channel, Ambipolar, and p‐Channel Organic Heterojunction Transistors Fabricated with Various Film Morphologies (Adv. Funct. Mater. 3/2007)
Author(s) -
Shi J. W.,
Wang H. B.,
Song D.,
Tian H. K.,
Geng Y. H.,
Yan D. H.
Publication year - 2007
Publication title -
advanced functional materials
Language(s) - English
Resource type - Reports
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.200790011
Subject(s) - heterojunction , materials science , ambipolar diffusion , optoelectronics , layer (electronics) , nanotechnology , semiconductor , field effect transistor , transistor , electron , electrical engineering , voltage , physics , engineering , quantum mechanics
Simultaneous introduction of short‐range repulsive interactions between dissimilar colloidal particles and attractive interactions between like particles provides a general new route to fabricating self‐organizing bipolar devices. By identifying combinations of conductive device materials between which short‐range repulsive forces exist in the presence of an intervening liquid, electrochemical junctions can be self‐formed, as reported by Chiang and co‐workers on p. 379. The relationship between the performance characteristics of organic field‐effect transistors (OFETs) with 2,5‐bis(4‐biphenylyl)bithiophene/copper hexadecafluorophthalocyanine (BP2T/F 16 CuPc) heterojunctions and the thickness of the BP2T bottom layer is investigated. Three operating modes (n‐channel, ambipolar, and p‐channel) are obtained by varying the thickness of the organic semiconductor layer. The changes in operating mode are attributable to the morphology of the film and the heterojunction effect, which also leads to an evolution of the field‐effect mobility with increasing film thickness. In BP2T/F 16 CuPc heterojunctions the mobile charge carriers accumulate at both sides of the heterojunction interface, with an accumulation layer thickness of ca. 10 nm. High field‐effect mobility values can be achieved in continuous and flat films that exhibit the heterojunction effect.