High mobility vanadyl-phthalocyanine polycrystalline films for organic field-effect transistors

Abstract

The organic films of vanadyl-phthalocyanine (VOPc) compounds showed weak epitaxy growth (WEG) behavior on thin ordered para-sexiphenyl (p-6P) layer with high substrate temperature. The WEG of VOPc molecules standing up on the p-6P layer leaded to high in-plane orientation and their layer-by-layer growth behavior. In consequence, high quality VOPc films were obtained, which were consisted of lamellar crystals. Organic field-effect transistors with VOPc∕p-6P films as active layers realized high mobility of above 1cm2∕Vs. This result indicated that nonplanar compounds can obtain a device performance better than planar compounds, therefore, it may provide a rule to find disklike organic semiconductor materials.

π-Conjugated molecules with fused rings for organic field-effect transistors: design, synthesis and applications

“…CuPc, CoPc, FePc, MnPc, NiPc, and ZnPc). Of these, copper phthalocyanine (CuPc, (55)) is one of the most widely used molecules for OFETs with a maximum field-effect mobility of 0.02 cm (57) 35 , and VOPc (58) 36 have been discovered to possess high p-type field-effect properties. In contrast, it should be noted that tin (IV) phthalocyanine oxide (SnOPc, (59)) was found to be an interesting air-stable n-type OFET material which contains no electron-withdrawing groups.…”

Growth of Large Crystalline Grains of Vanadyl‐Phthalocyanine without Epitaxy on Graphene

“…The average value of the mobility is roughly twice as high for the HT compared to the RT (0.27 ± 0.04 cm 2 V −1 s −1 for HT and 0.14 ± 0.08 cm 2 V −1 s −1 for RT) and is consistent with prior reports of high mobility in VOPc. [ 21,23 ] The average value of γ decreases from (−1.2 ± 0.2) × 10 −4 m 1/2 V −1/2 for RT to (−1.7 ± 0.1) × 10 −4 m 1/2 V −1/2 for the high temperature deposition, which suggests a decrease in trapping for the HT sample. The comparatively high mobility value for the HT sample is despite the VOPc being "stood up" relative to the graphene which should increase charge transport laterally through the fi lm (as in a OTFT measurement) rather than vertically through it as probed here.…”

“…Despite this, the VOPc island size seen here is still larger than that reported for VOPc deposited onto an orderinducing p-6P layer on silicon oxide. [ 21 ] This suggests that high quality OSC thin fi lm deposition can be achieved on graphene without the need for order-inducing layers.…”

“…[1][2][3][4][5] Organic semiconductors (OSCs) have been used as the active layers in organic photovoltaics (OPVs) [ 6 ] or para-sexiphenyl (p-6P) [ 22 ] have both been used to structurally modify MPc fi lms. For VOPc, elevated substrate temperatures have been used for morphological control when depositing onto CuI, [ 11 ] silicon oxide, [ 23 ] and p-6P on silicon oxide, [ 21 ] and when codeposited with C60 onto a C60 layer. [ 14 ] Graphene is an attractive electrode for organic electronics due to its strength, fl exibility, and conductivity.…”

“…[ 21 ] However, morphology and crystallinity are also substrate dependent; for example, templating layers such as CuI [ 11 ] The performance of organic semiconductor thin fi lms in electronic devices is related to their crystal structure and morphology, with charge transport mobility dependent on the degree of crystallinity and on the crystallographic orientation. Here organic molecular beam deposition of vanadyl phthalocyanine is studied on graphene and it is shown that crystalline grains up to several micrometers across can be formed at substrate temperatures of 155 °C, compared to room temperature grain sizes of ≈30 nm.…”