A comparative study of organic single-crystal transistors gated with various ionic-liquid electrolytes

Abstract

We report on a comparative study of rubrene single-crystal field-effect transistors with various ionic-liquid electrolytes used for gate insulators. A systematic correlation is found that mobility of the field-effect transistors increases with decreasing electrostatic capacitance of the electric double layers, as the result of highly reproducible comparisons among tens of samples with the variation of anions in the purified ionic liquids. By optimizing the gating ionic liquid, the highest mobility of the electrolyte-gated organic transistors elevated up to 9.5 cm2/V s, which is only a fraction of the value of intrinsic material property, demonstrating an excellent field-effect switching operation.

High-performance n-type organic field-effect transistors with ionic liquid gates

“…To this end, we have fabricated N , NЉ-bis͑n-alkyl͒-͑1,7 and 1,6͒-dicyanoperylene-3,4:9,10-bis͑dicarboximide͒s ͑PDIF-CN 2 ͒ single-crystal transistors with IL, using the same methods used for p-type rubrene single crystals. 16,17 As organic material we have selected PDIF-CN 2 , 19,20 which exhibits the highest electron mobility reported to date ͑1-6 cm 2 / V s͒. 21 We show that the electron mobility of PDIF-CN 2 single-crystal transistors with IL ͑as high as 5.0 cm 2 / V s in air͒ is comparable to the corresponding devices without IL, thus having air as gate dielectric.…”

“…For p-type transistors ͑based on rubrene͒ it was also recently found that the surface of organic semiconductors is not damaged by the ILs, and mobility values up to 9.5 cm 2 / V s can be achieved by selecting the proper IL. 17 For n-type OFETs with EDL gating, however, virtually nothing is known at this stage.…”

“…Indeed, for p-type transistors, the operation of high-quality OFETs based on EDL gating has been recently reported by several groups. [8][9][10][11][12][13][14] Among all investigated EDLOFETs, room temperature ionic liquids ͑ILs͒ are particularly promising, [15][16][17][18] as they have shown to enable a very fast response ͑compared to other types of electrolytes͒ to changes in the gate voltage. For p-type transistors ͑based on rubrene͒ it was also recently found that the surface of organic semiconductors is not damaged by the ILs, and mobility values up to 9.5 cm 2 / V s can be achieved by selecting the proper IL.…”

“…For rubrene OFETs it has been demonstrated that the charge carrier mobility is larger when the capacitance of the IL is smaller. 17 We have therefore selected ͓P13͔͓TFSI͔ for our investigations, since this compound has the smallest capacitance among all ILs which we have worked with. Note that this compound is also expected to absorb less water as compared to others ILs, because of the strong hydrophobicity of the fluoroterminated anion, which makes it particularly favorable for investigating n-type OFETs.…”

Electric-Field-Induced Superconductivity on an Organic/Oxide Interface

“…18,19) This configuration has attracted interest for an organic polymer FET with a polymer electrolyte solution with high on-state conductance 20,21) and an organic single crystal FET with low on-state gate bias. [22][23][24][25] An oxide FET device with an electrolyte solution was first reported on ZnO and a polymer electrolyte, and high-density carrier accumulation was also reported for a device with an ionic liquid as an electrolyte. 26,27) The device configuration is schematically illustrated in Fig.…”