Chapter Interlayer Processing in Active Matrix OLED Displays

Medical genetic

Interlayer Processing in Active Matrix OLED Displays

Medical genetic

Organic RFID Tags

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Low-temperature and low-voltage, solution-processed metal oxide n-TFTs and flexible circuitry on large-area polyimide foil

In this article, we report on high-performance solution-based n-type metal oxide TFTs processed directly on polyimide foil and annealed at 250 °C. Saturation mobilities exceeding 2 cm²/(Vs) and Ion/Ioff ratios beyond 108 have been achieved. Using these oxide n-TFTs, fast and low-voltage flexible circuitry is presented. Furthermore, a complete 8-bit RFID transponder chip, containing 294 oxide n-TFTs has been fabricated. Both high-speed and low-voltage operation makes the presented oxide n-TFT technology suited for both the pixel driving and embedded line-drive circuitry at the borders of flexible AMOLED displays

Design and manufacturing of organic RFID circuits Coping with intrinsic parameter variations in organic devices by circuit design

A detailed study of device characteristics and parameter variations of organic transistors on foil leads to the conclusion that design of p-type only digital circuits needs to focus on optimal yield, rather than on speed. From this perspective, subsequent generations of organic RFID tags have been realized, by increasing complexity (from 64 bit to 128 bit code generators), by adding functionality (Manchester encoding, anti-collision protocols), and by increasing data rate of the generated ID code (from 752 bits per second towards 50 kbit per second). As such, each of the requirements towards EPC compatible organic RFID tags is shown independently in code generators on foil, but not yet in a single RFID tag.status: publishe

Adhesion promoting polymerinterlayers for Ag layers deposited in OLED processing

One of the main drivers for organic electronic research are the backplanes for flexible active-matrix displays using organic light-emitting diodes (AM-OLEDs). In our work, we processed organic thin-film transistors (OTFTs) at low temperatures (<160 degrees C) on poly(ethylene naphthalate) (PEN) foils. There are several challenges in the integration of OLEDs on top of OTFT backplanes on a foil. One of them is the interlayer between the OTFT backplane and the OLEDs. For this layer, low-temperature crosslinkable, chemically resistant polymers are required, which, on the one hand, provide proper electrical insulation to OTFT and OLED devices and, on the other hand, can be processed reliably and provide good adhesion to the OLED anode. From the point of reflectivity and, therefore, light emission efficiency, Ag would be a preferred option. The challenge from the processing point of view is the poor adhesion of evaporated or e-beam deposited Ag on most surfaces. Commonly used microelectronic approaches such as sputtered metal or Ar pre-sputtering cannot be applied because of resulting surface leakage paths on the organic dielectric caused by dangling bonds. To address this issue, we tested a variety of low-temperature crosslinkable polymers (e.g., SU-8, parylene) regarding adhesion, roughness and processability and we measured the adhesion of the Ag deposited at different thicknesses using the Scotch tape test (ASTM D 3359). The best adhesion properties were obtained with parylene N allowing Ag layers with thicknesses up to 200 nm and surface roughness around 7-8 nm.status: publishe

Reconfigurable neuromorphic synapse interconnects with TFTs

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An integrated double half-wave organic Schottky diode rectifier on foil operating at 13.56 MHz

We demonstrate an integrated organic double half-wave rectifier for use in organic radio frequency identification (RFID) tags. This rectifier comprises two organic Schottky diodes, each followed by a capacitor, integrated on the same foil. This rectifier delivers approximately twice the dc voltage of single half-wave rectifiers. Its offset voltage is merely 2 V. It is able to generate voltages of 10-14 V, which are necessary for driving current organic RFID multibit code generators, from an ac-input voltage of only 8-10 V amplitude, which are generated at rf magnetic fields of 0.9-1.3 A/m. Such fields are below the minimum required rf magnetic field strength set by standards. (C) 2008 American Institute of Physics.status: publishe

Functional Pentacene Thin Films Grown by In-Line Organic Vapor Phase Deposition at Web Speeds above 2 m/min

We show in this paper that the organic vapor phase deposition technique can advantageously be extended to an in-line system, where a susceptor moves at a constant speed underneath an elongated showerhead. Highly uniform pentacene films are grown at web speeds of up to 2.1 m/min, equivalent to an average deposition rate of 105 angstrom/s in a static system. These pentacene films are of high electrical quality as proven by transistor mobilities of up to 1.5 cm(2) V-1 s(-1) and five-stage ring oscillators on foil that achieve a frequency of 24 kHz at a supply voltage of 20 V. (C) 2009 The Japan Society of Applied Physic

Nucleation of organic semiconductors on inert substrates

We have adapted the microscopic theory of nucleation for the epitaxial growth of inorganic materials to the nucleation of organic small molecules on an inert substrate like the gate dielectric of an organic thin-film transistor. The parameters required to explore the model were calculated with the standard MM3 force field and also include experimentally determined vapor pressure data, as well as film growth data. Sufficient agreement is found between the experimentally determined equilibrium crystal shape and heats of sublimation on the one hand and the calculated parameters on the other hand. The growth of pentacene, tetracene, and perylene on inert substrates has been studied in terms of this theory, especially focusing on the two-dimensional (2D) to 3D nucleation transition. It is demonstrated that 3D nucleation leads to ill-connected grains, while 2D nucleated grains form continuous films suitable for charge transport. The analysis of this transition allows for the experimental determination of the molecule-substrate interactions for a given molecule on a given surface. It was found that the deposition conditions for 2D growth shift to less favorable substrate temperatures and deposition rates as the difference between interlayer interactions and molecule-substrate interactions increase and the intralayer interactions decrease. Moreover, those interactions affect the nucleation rate and therefore the ultimate 2D grain size that can be obtained. © 2003 The American Physical Society.status: publishe