Frontiers of Engineering Reports on Leading-Edge Engineering from the 2013 Symposium (2014) / Chapter Skim
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Materials and Process Engineering for Printed and Flexible Optoelectronic Devices--Antonio Facchetti
Materials and Process Engineering for Printed and Flexible Optoelectronic Devices--Antonio Facchetti
Pages 113-126
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From page 113... ...
. Applications such as flexible displays, plastic radio frequency identification tags, disposable diagnostic devices, rollable solar cells, and simple consumer products and games represent a future multibillion-dollar market.
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From page 114... ...
Conventional Electronics Organic/Printed Electronics Advantage or disadvantage High performance Low performance Small area/feature size Large area/feature size High cost/unit area Low cost/unit area High capital investment Low capital investment Long production run Short production run Durable Disposable Rigid Flexible Selected markets Everywhere Photolithography Printing Materials Semiconductor, conductor, dielectric, passive, substrate Devices/applications Transistors, circuits, memory, diodes, sensors, displays, batteries, photovoltaics, conductive traces, antennas, resistors, capacitors, inductors
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From page 115... ...
as small as possible. The carrier mobility of printable semiconductors is about two orders of magnitude lower than that of crystalline inorganic materials, and typical resolution for the OFET channel length in printed devices is larger by the same order of magnitude.
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From page 116... ...
Metal cathode g pp I Interlayer Semiconductor Donor-Acceptor Blend Interlayer ITO anode Flexible Modules Power Textiles Power Window Substrate FIGURE 1 Structure of an organic field-effect transistor and photovoltaic cell and corresponding applications. ITO = tin-doped indium oxide; .
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From page 117... ...
The major obstacle to printed RFID applications is to achieve high circuit frequency operation and enable efficient rectification (convert the ac-voltage detected and generated by the antenna at the targeted base carrier frequency to a dc voltage)
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From page 118... ...
Throughputs greater than 1 m2/s are considered "high volume"; most printing methods fall in this category. There are several considerations to determine what process can be used based mainly on the viscoelastic properties of materials and the desired feature sizes (lateral resolution, film thickness, surface morphology, surface energy)
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From page 119... ...
(m2/s) Issues Materials Printed Lithography (10–4)
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From page 120... ...
It can also be used to print thick dielectric layers and passive materials for device encapsulation. Indeed, the first report of a "printed organic thin film transistor" described screen-printed carbon paste electrodes for source, drain, and gate contacts (Horowitz et al., 1996)
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From page 121... ...
Electronic Materials Printed electronic devices need a set of core materials for charge accumulation, injection, and transport as well as specific materials to enable particular device functions (Facchetti 2013; Facchetti et al.
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From page 122... ...
Ion:Ioff > 106 Ion:Ioff > 106 Ion:Ioff > 106 BF > 6 MV/cm BF > 5 MV/cm Current Ag, Au, Cu PEDOT:PSS; Fused thiophenes; Polythiophenes; In2O3, ZnO, IZO, PMMA; Sol-gel oxides; materials nanoparticles; PANI; Polymer + Heteroarenes; Naphthalene IGZO P-UV; Oxides-epoxy ITO CNT; Graphene Perylenes diimides; Cross-linked DPPs PVP Advantages Good Good Easy purification; Easy ink High mobility Easily Tunable processability; processability; Facile scale-up formulation printable permittivity High Sufficient conductivity conductivity Limitations Costly Low-speed Difficult ink Difficult High processing Low Leaky; application formulation for purification; temp; Few permittivity; Rough surface; printing; Few n-channels p-channels High Thick films Ambient stability available; available; Ambient permeability; Limited ambient stability Thick films stability Next- Reduce cost Enhance Increase m Increase m Reduce T; enhance Reduce film Enhance generation conductivity uniformity thickness printability targets NOTE: s = conductivity; m = charge carrier mobility; Ag = silver; Au = gold; BF = breakdown field; CNT = carbon nanotube; Cu = copper; DPP = diketopyrrolopyrrole; IZO = indium-zinc-oxide; IGZO = indium-gallium-tin-oxide; ITO = tin-doped indium oxide; J = leakage current density; PANI = polyaniline; PMMA = poly(methylmetacrylate) ; PEDOT:PSS = polyethylenedioxothiophene:polystyryl sulphonate; P-UV: A UV-vis crosslinkable polymer; PVP = poly(vinylphenole)
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From page 123... ...
The charge transport in organic semiconductor films is highly dependent on the film deposition conditions -- printing process, solvent used in formulating the ink, active/ additive component concentrations, deposition temperature, substrate morphology, and surface energy. Environmental conditions during film deposition can also affect materials performance, although some organic semiconductors are air stable and do not require a controlled environment during film processing.
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From page 124... ...
Furthermore, the dielectric film surface in contact with the semiconductor should be very smooth. Because charge transport in organic semiconductors is confined in the semiconductor within a few nanometers of the semiconductor-dielectric interface, rough interfaces generate charge scattering and reduce carrier mobility.
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From page 125... ...
, high-performance solution-deposited semiconducting films over a large area, and temporal performance stability. Despite these difficulties, initial important successes in device fabrication using organic materials and roll-to-roll processes are encouraging and several companies strongly believe that organic electronics is already a reality.
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