Options
2010
Presentation
Titel
OLED-on-CMOS for microdisplays. Technology, design, applications
Titel Supplements
Presentation held at Plastic Electronics, PE 2010, October 19-21, 2010, Dresden
Abstract
Integration of organic light-emitting diodes (OLED) onto silicon substrates (wafers) allows embedding highly efficient emitters CMOS integrated circuitry (IC) and therefore novel optoelectronic devices for (micro-)displays and sensors. Based on that combination various requirements regarding design and technology interfaces arise, e.g., on OLED device modelling, interaction of active CMOS and OLED devices, electro-optical simulation and testing, CMOS/OLED material and structure interface. Moreover, certain applications demand strong area minimization of underlying analog circuitry, specifically pixel cells in OLED microdisplays. "Microdisplays" are usually referred to as very small displays featuring a screen diagonal <1", that require optical magnification to be resolved by the human eye. Thus, microdisplays based on OLEDs can be used for Near-To-Eye (NTE) applications such as viewfinders, head mounted displays (HMD) and as mentioned in [1] also for microprojection units. The maximum luminance for these applications can range from 100 Cd/m² for non-see-through video glasses and viewfinders, up to 10,000 Cd/m² for see-through applications or even more for microprojection units. Requirements for microdisplay backplanes, which can cover all of these applications, are small pixel pitch (<15µm), small display size (<0.6"), low power consumption (few mW), good linearity between video input signal and light output (grayscale), good homogeneity of the display luminance and possibly - depending on application-specific luminance - high driving voltage capability (up to 10 V) of the pixel circuit. Since active CMOS devices (transistors...) are already part of the OLED microdisplay backplane for driving its pixels, integration of CMOS-inherent sensors appears obvious. Specifically adding optical sensors (e.g., CMOS photodiodes) to the OLED emitters allows completely new features for microdisplays. A so-called bi-directional OLED microdisplay combines a display matrix and a camera on a single chip, enabling interactive displays [2]. Embedded into a NTE setup such microdisplay projects an image onto the user's eye, and in optically opposite direction is capable in detecting the users's eye and its conscious and unconscious movements, therefore performing gaze control and interaction with the display content. The presentation provides an overview on technology, design and application.