Simon Dominic Ogier

Organic light emitting diodes

Organic light emitting diode (LED) technology has reached a point where performance levels are adequate for a number of applications. This review examines the key scientific issues that underlie the operation of such LEDs. The most advanced LEDs are multilayer devices, with the different layers possessing specialized carrier transport/optical properties. A combination of these materials results in the highly efficient devices that have now been reported by several laboratories. The important issue of reliability and some possible applications for organic LEDs are surveyed.An organic light emitting diode with dielectric barriers (120, 106) at both the anode-organic and the cathode-organic interfaces.

Organic electronic devices

The present invention comprises a substantially organic layer comprising a first electrode, between the second electrode and the first electrode and the second electrode, a compound of formula (I), in (I), A [Formula 1]

Polymer-based organic field-effect transistor using offset printed source/drain structures

Organic field-effect transistors were fabricated using offset printed source/drain structures. Interdigitated electrode structures were printed with a poly(3,4–ethylenedioxythiophene) (PEDOT) formulation. A polymeric semiconductor polytriarylamine and different insulator layers were deposited by spin coating. A field-effect mobility of 3×10−3cm2V−1s−1 and on/off ratio of about 103 was achieved, making it possible to produce digital logic elements.

A novel gate insulator for flexible electronics

Abstract Field effect transistors using a poly(triaryl amine) p-channel organic semiconductor in conjunction with anodised aluminium oxide as the gate insulator (Al2O3 on Al) are demonstrated. Anodised films are pinhole-free, homogenous oxide layers of precisely controlled thickness. The anodisation process requires no vacuum steps; anodised Al2O3 is insoluble in organic solvents, and Al films are cheaply available as laminates on flexible substrates. Anodised Al2O3 is confirmed to have high gate capacitance (≈60 nF/cm2) and electric breakdown strength (>3 MV/cm in the working device). This property profile answers to the demands on gate insulators for flexible electronics applications.

High performance, acene-based organic thin film transistors

1,4,8,11-Methyl-substituted 6,13-triethylsilylethynylpentacene shows extended pi-pi overlap when deposited from solution, yielding organic thin film transistors with high and reproducible hole mobility with negligible hysteresis.

Gate insulators influencing electronic transport in organic FETs

New findings are presented relating to the optimal choice of gate insulators in organic field effect transistors (OFET). It was recently found that some organic semiconductors operate better when low-k materials are used in the gate. This is quite contrary to the conventional trend to use high permittivity dielectrics for low voltage operation. Interaction between the insulator and the semiconductor materials plays an important role in carrier transport. On one hand, the insulator is often responsible for the morphology of the semiconductor layer, but on the other hand it can also change the distribution of states by local polarisation effects. Carrier localisation is enhanced by insulators with large permittivities, due to the random dipole field present at the interface. We have investigated this effect on a number of disordered organic semiconductor materials and show here that the use of low-k materials may lead to improvements in mobility, reduced temperature activation and hysteresis. In particular, the behaviour of the threshold voltage is interesting. The differences in the underlying physics compared to the case of FETs based on band-like semiconductors, is also discussed.

Air Stable, Amorphous Organic Films and their Applications to Solution Processable Flexible Electronics

The rapidly expanding field of organic semiconductors for display and low-cost electronic applications requires materials, which not only have high mobility but also benefit from solution processability and environmental stability. In this paper we present a new class of solution coatable organic materials with excellent stability to air and light. Spin-coated FET devices operate at ambient conditions without encapsulation and show p-type field-effect mobilities of 2 x 10 -3 cm 2 V -1 s -1 and on/off ratios greater than 10 4 . Thin films can be deposited from common organic solvents onto a variety of substrates. These films are mechanically robust and can withstand temperatures in excess of 100 °C without significant changes in electrical performance. FET switching and transient characteristics at higher frequencies are also discussed. These types of materials should find applications in many areas of flexible electronics.