Controlling of the surface energy of the gate dielectric in organic field-effect transistors by polymer blend

Abstract

In this letter, we demonstrate that by blending insulating polymers, one can fabricate an insulating layer with controllable surface energy for organic field-effect transistors. As a model system, we used copper phthalocyanine evaporated on layers of polymethyl metacrylate blended with polystyrene with different blending ratios and measured the field-effect mobility in transistors. We show that the highest field-effect mobility is achieved for identical surface energies of the dielectric and the semiconductor. This simple technique demonstrates the viability of using the blends of insulating polymers to systematically control the surface energy of the gate dielectric toward achieving better performances.

Interfacial Heterogeneity of Surface Energy in Organic Field‐Effect Transistors

“…[16][17][18] In previous literature, the surface energy is usually calculated by measurements of contact angles at different points on the surface. [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] However contact angle measurements is a 'statistic-average' method that can only indicate differences at a millimeter level, and obviously cannot describe whether or not the interfacial state is homogeneous on the nanometer scale. [16][17][18][19][20][21][22][23] The latter is crucial, because the surface energy of the dielectric mainly infl uences the performances of OFETs at the interface on just such a nanometer scale.…”

Electrical and dielectric properties of foam injection-molded polypropylene/multiwalled carbon nanotube composites

“…Another approach that has been very recently proposed is to use percolative polymer nanocomposites filled with highly conductive additives such as carbon nanotubes [1,2,4]. In percolative nanocomposites, even though ε' significantly increases near the percolation threshold, this increase is usually accompanied with a huge increase in tan δ, due to the sharp insulation-conduction transition, which restricts their application toward dielectrics.…”

“…Recently, polymer-based composites have been tried as dielectrics for charge storage applications in capacitors and organic circuit boards [1][2][3][4][5][6][7][8]. Such composites should exhibit high dielectric permittivity (ε') and low dielectric loss (tan δ) to be an effective dielectric [1][2][3][4][5].…”

“…In percolative nanocomposites, even though ε' significantly increases near the percolation threshold, this increase is usually accompanied with a huge increase in tan δ, due to the sharp insulation-conduction transition, which restricts their application toward dielectrics. Some researchers have tried to come up with strategies to resolve this issue [1,2,4]. Yang et al coated MWCNTs with polypyrrole by an inverse micro-emulsion polymerization to screen charge movement and shut off leakage current [1].…”

“…Such composites should exhibit high dielectric permittivity (ε') and low dielectric loss (tan δ) to be an effective dielectric [1][2][3][4][5]. However, the dielectric permittivity of polymers is very low (e.g., ε' of PP < 3) and achieving a high ε' and low tan δ in a polymer system remains challenging [1][2][3][4][5][6][7][8]. One approach is to add ceramic fillers, which can increase ε' of polymer by about ten times at loadings close to 50 vol.% [6][7][8].…”