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OLED-on-Silicon technology has become vital to emissive microdisplays in near-to-eye displays, e.g., upcoming smart glasses. High-resolution OLED micro-patterning, embedded sensors and emission spectra outside the visible enable advanced features. Low-power active-matrix circuitry CMOS backplane architecture broadens the application range. Recent developments will be reported here.

Wearable augmented-reality (AR) has already started to be used productively mainly in manufacturing industry and logistics. Next step will be to move wearable AR from "professionals to citizens” by enabling networked, everywhere augmented-reality (in-/outdoor localisation, scene recognition, cloud access,…) which is non-intrusive, exhibits intuitive user-interaction, anytime safe and secure use, and considers personal privacy protection (user’s and others). Various hardware improvements (e.g., low-power, seamless interactivity, small form factor, ergonomics,…), as well as connectivity and network integration will become vital for consumer adoption. Smart-Glasses (i.e., near-to-eye (NTE) displays) have evolved as major devices for wearable AR, that hold potential to become adopted by consumers soon. Tiny microdisplays are a key component of smart-glasses, e.g., creating images from organic light emitting diodes (OLED), that have become popular in mobile phone displays. All microdisplay technologies on the market comprise an image-creating pixel modulation, but only the emissive ones (for example, OLED and LED) feature the image and light source in a single device, and therefore do not require an external light source. This minimizes system size and power consumption, while providing exceptional contrast and color space. These advantages make OLED microdisplays a perfect fit for near-eye applications. Low-power active-matrix circuitry CMOS backplane architecture, embedded sensors, emission spectra outside the visible and high-resolution sub-pixel micro-patterning address some of the application challenges (e.g., long battery life, sun-light readability, user interaction modes) and enable advanced features for OLED microdisplays in near-to-eye displays, e.g., upcoming connected augmented-reality smart glasses. This report is to analyze the challenges in addressing those features and discuss solutions.

An approach for direct electron beam micropatterning is presented, whereby the emission of an organic light-emitting diode (OLED) can be modified at high-resolution by using a focused electron beam through its encapsulation. By subsequent thermal annealing it is possible to tune the optical and electrical properties of the OLED.

We report on organic $p\text{\ensuremath{-}}i\text{\ensuremath{-}}n$ homojunctions composed of differently doped vacuum-deposited pentacene layers. We observe a remarkably high built-in voltage of 1.65 V. An analysis of the current-voltage characteristics under dark and illuminated conditions reveals that the open-circuit voltage is directly related to the built-in voltage and that the recombination process is influenced by the distinct charge transport properties of electrons and holes in the pentacene film. By a comparison with $p\text{\ensuremath{-}}i\text{\ensuremath{-}}p$ and $n\text{\ensuremath{-}}i\text{\ensuremath{-}}n$ single-carrier homojunctions, deep trap states located around 0.63 eV below the electron transport level are shown to influence the properties.

OLED can be applied as highly efficient and high-resolution patternable illumination source for controllable and steerable backlights, e.g., for use in autostereoscopic displays. To evaluate technology and approach a 3.5” 3D QVGA display prototype has been developed and combines several achievements: large-area OLED backlight, highly-efficient and fast-response OLED top-emitter, striped patterned backlight, individual electronic driving for adaptive backlight control and 3D mobile display application.

Near-to-eye (NTE) projection is the major approach to "Smart Glasses", which have gained lot of traction during the last few years. Micro-displays based on organic light-emitting diodes (OLEDs) achieve high optical performance with excellent contrast ratio and large dynamic range at low power consumption, making them suitable for such application. In state-of-the-art applications the micro-display typically acts as a purely unidirectional output device. With the integration of an additional image sensor, the functionality of the micro-display can be extended to a bidirectional optical input/output device, aiming for implementation of eye-tracking capabilities in see-through (ST-)NTE applications to achieve gaze-based human-display-interaction. This paper describes a new bi-directional OLED microdisplay featuring SVGA resolution for both image display and acquisition, and its implementation with see-through NTE optics.

Recently, bilayer resist processing combined with development in hydrofluoroether (HFE) solvents has been shown to enable single color structuring of vacuum-deposited state-of-the-art organic light-emitting diodes (OLED). In this work, we focus on further steps required to achieve multicolor structuring of p-i-n OLEDs using a bilayer resist approach. We show that the green phosphorescent OLED stack is undamaged after lift-off in HFEs, which is a necessary step in order to achieve RGB pixel array structured by means of photolithography. Furthermore, we investigate the influence of both, double resist processing on red OLEDs and exposure of the devices to ambient conditions, on the basis of the electrical, optical and lifetime parameters of the devices. Additionally, water vapor transmission rates of single and bilayer system are evaluated with thin Ca film conductance test. We conclude that diffusion of propylene glycol methyl ether acetate (PGMEA) through the fluoropolymer film is the main mechanism behind OLED degradation observed after bilayer processing.

Bulk heterojunction organic solar cells with a vertical variation of the C60:ZnPc composition within the absorption layer have been fabricated. The resulting gradient layer has been characterized by UV/vis transmission and reflection spectroscopy. Depending on the mixing strategy, the formation of higher aggregated ZnPc species can be initialized earlier in a blended thin film. The gradient strength has been varied and its influence on the solar cell performance has been determined. A variation of the absorption layer thickness has been carried out to investigate a possible charge carrier transportation improvement. In order to explain the positive effect of a graded structure within the absorption layer, detailed voltage-dependent spectral response measurements have been performed. It is shown that not only the absorption behavior of the cell is improved, but also the charge carrier transportation properties.

To leverage the potential of organic solar cells, suitable materials for the photoactive layers have to be found. Herein, we show that the well-known fluorescent dye 3-(2′-benzothiazolyl)-7-diethylaminocoumarin works as an efficient light absorber material with a sensitivity at wavelengths from 400 to 650 nm. In combination with doped transport layers and optimization of the photodiode stack, a power conversion efficiency up to 1.9% under air mass 1.5 and 100 mW/cm 2 illumination could be achieved.

We present a QQVGA top emitting monochrome AMOLED display with 85dpi resolution using an organic TFT backplane on low temperature PEN-foil. The backplane process flow is based on a 7 layer photolithography process that yields a final mobility of the OTFT of ∼0.4 cm2/Vs. The aperture ratio of the top-emitting OLEDs is over 75%. For operation at 10 V supply voltage (VDD), the brightness of the display using red and green OLEDs exceeds 200 cd/m2.

We present our recent achievements in organic semiconductor technology in two emerging application areas. We show that the performance of our technology approaches the requirements for Electronic Product Coding RFID tags. Also, backplanes of OLED displays are enabled by the unique compatibility of pentacene transistors with high-k gate dielectrics. © 2009 IEEE.