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Fabrication of Poly(triaryl amine) Field-effect Transistors

PTAA Description

Poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA; 702471) is an amorphous p-type polymer semiconductor.1, 2 It may be used to fabricate field-effect transistors (FETs). PTAA is also useful as a hole transport material in organic light emitting diodes (OLEDs).

Poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine]

Procedure for Fabrication of PTAA Field-effect Transistors

Bottom-gate bottom-contact field-effect transistors (FETs) were fabricated in a nitrogen atmosphere on highly doped Si-wafers with a thermally grown 250 nm SiO2 layer. The two layers served as the gate electrode and gate insulator. Au source and drain electrodes (30 nm thick) were defined by standard photolithography:

channel length (L) = 10 mm
channel width (W) = 10 mm

Before deposition of the PTAA polymer layer, the Si-wafers were treated with octyltrichlorosilane (OTS-18; 104817 ) by immersing them in 10 mM solutions in toluene for 15 minutes at 60 °C.

A homogeneous solution of PTAA was prepared in toluene at room temperature containing 1.0 wt% of the polymer. This solution was deposited via spin-coating at 500 rpm for 30 seconds followed by 2,000 rpm for 50 seconds.

Results

Electrical characterization of the PTAA FETs was conducted in a nitrogen atmosphere with a HP4155B semiconductor parameter analyzer. Field-effect mobilities were calculated from transfer characteristics (saturation regime) employing the relation:3

Equation

Isd is the source-drain current (saturation regime)
Vg and Vsd gate and soxce-drain voltage, respectively
Ci the insulator capacitance
W and L the channel width and length
V0 the turn-on voltage

Transfer and output curves for PTAA transistors are shown in Figures 1 and 2.

Transfer output curves for PTAA transistors corresponding to field effect mobility of 4 x 10–3 cm2/Vs.

Figure 1.Transfer output curves for PTAA transistors corresponding to field effect mobility of 4 x 10–3 cm2/Vs.

Output curves for PTAA transistors corresponding to field effect mobility of 4 x 10–3 cm2/Vs.

Figure 2.Output curves for PTAA transistors corresponding to field effect mobility of 4 x 10–3 cm2/Vs.

Materials
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References

1.
Chabinyc ML, Jimison LH, Rivnay J, Salleo A. 2008. Connecting Electrical and Molecular Properties of Semiconducting Polymers for Thin-Film Transistors. MRS Bull.. 33(7):683-689. http://dx.doi.org/10.1557/mrs2008.140
2.
Veres J, Ogier S, Leeming S, Cupertino D, Mohialdin Khaffaf S. 2003. Low-k Insulators as the Choice of Dielectrics in Organic Field-Effect Transistors. Adv. Funct. Mater.. 13(3):199-204. http://dx.doi.org/10.1002/adfm.200390030
3.
Brown A, Jarrett C, de Leeuw D, Matters M. 1997. Field-effect transistors made from solution-processed organic semiconductors. Synthetic Metals. 88(1):37-55. http://dx.doi.org/10.1016/s0379-6779(97)80881-8

Data courtesy of Dr. Iain McCulloch, Imperial College London and Flexink, Inc.