The impact of carbon sp2 fraction of reduced graphene oxide on the performance of reduced graphene oxide contacted organic transistors

Abstract

One of the major bottlenecks in fabricating high performance organic field effect transistors (OFETs) is a large interfacial contact barrier between metal electrodes and organic semiconductors (OSCs) which makes the charge injection inefficient. Recently, reduced graphene oxide (RGO) has been suggested as an alternative electrode material for OFETs. RGO has tunable electronic properties and its conductivity can be varied by several orders of magnitude by varying the carbon sp2 fraction. However, whether the sp2 fraction of RGO in the electrode affects the performance of the fabricated OFETs is yet to be investigated. In this study, we demonstrate that the performance of OFETs with pentacene as OSC and RGO as electrode can be continuously improved by increasing the carbon sp2 fraction of RGO. When compared to control palladium electrodes, the mobility of the OFETs shows an improvement of ∼200% for 61% sp2 fraction RGO, which further improves to ∼500% for 80% RGO electrode. Similar improvements were also observed in current on-off ratio, on-current, and transconductance. Our study suggests that, in addition to π-π interaction at RGO/pentacene interface, the tunable electronic properties of RGO electrode have a significant role in OFETs performance.

Synthesis and Characterization of Reduced Graphene Oxide and Their Application in Dye-Sensitized Solar Cells

“…The synthesis of reduced graphene oxide (rGO) suspension used in the study was done via the chemical reduction of individual graphene oxide (GO) sheets as described in our previous publications [39][40][41][42]. The individual GO sheets in powdered form were obtained from Cheap Tubes Inc., Cambridgeport, VT. Thirty milligrams of GO powder was added to a 30 mL of deionized (DI) water in a vial.…”

Effect of contact resistance in organic field‐effect transistors

“…[ 89 ] Although the WF of Au is close to the HOMO of pentacene, the strong dipole effects produced a large hole injection barrier height at the Au/pentacene interface. [ 33 ] However, due to the edge‐on arrangement of pentacene molecules at the Ti 2 CT x /pentacene interface, there may not be strong interface dipole effects [ 92 ] , and the WF of Ti 2 CT x is not seriously affected. Therefore, according to the energy level alignment between Ti 2 CT x and pentacene (HOMO ≈ 5.2 eV), a low Φ B is expected.…”

Minimizing electrode edge in organic transistors with ultrathin reduced graphene oxide for improving charge injection efficiency

“…In designing an ultrathin electrode, single-layer graphene with a thickness of several angstroms would be a good choice, and this has successfully been utilized as an electrode for OFETs, [21][22][23][24][25] but it may suffer from difficulties in patterning over a large area. Graphene oxide (GO) with a thickness comparable to graphene has been demonstrated as a promising electrode candidate for OFET application, mainly because (i) GO shows good compatibility with organic semiconductors; [26][27][28][29][30][31] (ii) GO is low-toxicity and low-cost, which is highly promising for large-mass production; (iii) GO with many oxygen-containing groups in its basal plane and edge can be decorated with other functional groups for different applications, 32 unlike graphene with a relatively inert surface; (iv) GO is easily reduced to RGO, which is sometimes treated as graphene and has unique electrical, mechanical and optical properties. 33 Despite the above advantages, the thickness of GO or RGO electrodes currently used for OFETs is of the order of tens of nanometers, [26][27][28][29][30][31] which may produce a clear and wide electrode edge.…”

“…Graphene oxide (GO) with a thickness comparable to graphene has been demonstrated as a promising electrode candidate for OFET application, mainly because (i) GO shows good compatibility with organic semiconductors; [26][27][28][29][30][31] (ii) GO is low-toxicity and low-cost, which is highly promising for large-mass production; (iii) GO with many oxygen-containing groups in its basal plane and edge can be decorated with other functional groups for different applications, 32 unlike graphene with a relatively inert surface; (iv) GO is easily reduced to RGO, which is sometimes treated as graphene and has unique electrical, mechanical and optical properties. 33 Despite the above advantages, the thickness of GO or RGO electrodes currently used for OFETs is of the order of tens of nanometers, [26][27][28][29][30][31] which may produce a clear and wide electrode edge. In addition, most reported GO or RGO electrodes are physically adsorbed on the substrate [26][27][28][29][30][31] and may not have strong interface adhesion strength.…”