Solution processed tetrasubstituted zinc phthalocyanine as an active layer in organic field effect transistors

Abstract

Spun films of liquid crystalline peripheral-tetrasubstituted zinc (II) phthalocyanine (Pc) derivatives have been employed as active organic semiconducting layers in the fabrication of organic field effect transistors. The Pc molecules in the thin film formulation are stacked perpendicular to the substrate. Values of 1.8×10−4 cm2 V−1 s−1 and 103 were estimated for the field-effect mobility and on/off ratio, respectively, from the hysteresis-free transistor characteristics. The transistor can be switched on and off at a relatively low value of 3.7 V for threshold voltage. The carrier transport is believed to be largely determined by the multidomain Pc film structure.

Non‐Peripheral Tetrahexyl‐Substituted Vanadyl Phthalocyanines with Intermolecular Cofacial π–π Stacking for Solution‐Processed Organic Field‐Effect Transistors

“…However, the mobilities of the tetraalkoxy-substituted Pcs were very low (10 − 4 -10 − 3 cm 2 V − 1 s − 1 ). [ 22,23 ] A peripheral tetraalkyl-substituted OVPc exhibited a moderate mobility of 0.017 cm 2 V − 1 s − 1 , [ 11 ] which is still two orders of magnitude lower than that of unsubstituted OVPcs. [ 17 ] Several factors may cause the low mobility of the devices based on these soluble Pcs: 1) the introduction of substituents may alter the packing motif of Pc molecules, leading to a larger intermolecular distance and a smaller π -electron orbital overlap; [24][25][26][27] 2) the edge-on alignment of disc-like Pc molecules for the formation of charge transport channels along the source-drain electrodes direction is often diffi cult; [ 6 ] and 3) tetra-substituted Pcs are a mixture of four structural isomers, [ 12 ] which might remarkably reduce the order of the molecules in the fi lms.…”

“…Chemical structures of four isomers of non-peripheral tetrahexyl-substituted vanadyl phthalocyanine. The peripheral sites are labeled as 2, 3, 9, 10, 16, 17, 23, and 24, and the non-peripheral sites are numbered as 1,4,8,11,15,18,22, and 25. [ 12 ] Figure S4, Supporting Information).…”

High-mobility solution-processed copper phthalocyanine-based organic field-effect transistors

“…Liquid-crystal zinc (II) phthalocyanine and lutetium (III) bisphthalocyanine derivatives, both substituted with peripheral individual functional groups, were spin-coated at room temperature on SiO 2 /Si substrates as active layers of organic thin-film transistors because of easy solution-based formulation of supramolecular structures with the ability to design desired mesomorphic properties [29,30]. The post-deposition annealing of these compounds was found to be critical for controlling charge transport along a preferential direction.…”

ABAB‐Symmetric Tetraalkyl Titanyl Phthalocyanines for Solution Processed Organic Field‐Effect Transistors with Mobility Approaching 1 cm2 V−1 s−1

“…On the other hand, discotic conjugated molecules are believed to be promising solution processible OSCs since they have two‐dimensional (2D) conjugated cores and the molecules can self‐assemble into column nanostructures in which adjacent molecules experience a much large π‐orbital overlap for efficient charge transport 9. A number of solution processsible discotic OSCs have been synthesized for OFETs 10–19. However, so far only a few of them exhibit field‐effect mobility in the level of 10 −1 cm 2 V −1 s −1 12, 13…”

“…All these features imply that MPcs can be high mobility solution processible OSCs by introducing carefully selected solubilizing groups in the appropriate positions of Pc ring. In fact, various solution processible Pcs have been synthesized for OFET fabrication by placing substituents on the Pc ring at the peripheral or non‐peripheral benzo‐sites 12–19. But all these Pcs have substituents distributed in all four outer phenyl rings.…”