Olivier Prache

Microdisplays based upon organic light-emitting diodes

Microdisplays, some of which exploit the dense electronic circuitry in a silicon chip, are enabling a new wave of ultraportable information products, including headsets for viewing movies and cell phones with full-screen Internet access. This paper reports the approach to microdisplay development at eMagin Corporation. The requirements for microdisplays are reviewed, and the case is made that organic light-emitting diodes (OLEDs) are the best candidate transducer technology for meeting these requirements. A 1280 × 1024 (SXGA) monochrome OLED microdisplay is described as an example.

AMOLED (active matrix OLED) functionality and usable lifetime at temperature

Active Matrix Organic Light Emitting Diode (AMOLED) displays are known to exhibit high levels of performance, and these levels of performance have continually been improved over time with new materials and electronics design. eMagin Corporation developed a manually adjustable temperature compensation circuit with brightness control to allow for excellent performance over a wide temperature range. Night Vision and Electronic Sensors Directorate (US Army) tested the performance and survivability of a number of AMOLED displays in a temperature chamber over a range from -55°C to +85°C. Although device performance of AMOLEDs has always been its strong suit, the issue of usable display lifetimes for military applications continues to be an area of discussion and research. eMagin has made improvements in OLED materials and worked towards the development of a better understanding of usable lifetime for operation in a military system. NVESD ran luminance degradation tests of AMOLED panels at 50°C and at ambient to characterize the lifetime of AMOLED devices. The result is a better understanding of the applicability of AMOLEDs in military systems: where good fits are made, and where further development is needed.

Recent advances in small molecule OLED-on-silicon microdisplays

High resolution OLED-on-silicon microdisplay technology is unique and challenging since it requires very small subpixel dimensions (~ 2-5 microns). eMagins OLED microdisplay is based on white top emitter architecture using small molecule organic materials. The devices are fabricated using high Tg materials. The devices are hermetically sealed with vacuum deposited thin film layers. LCD-type color filters are patterned using photolithography methods to generate primary R, G, B colors. Results of recent improvements in the OLED-on-silicon microdisplay technology, with emphasis on efficiencies, lifetimes, grey scale and CIE color coordinates for SVGA and SXGA resolution microdisplays is presented.

53.3: High Performance Top Emitting Green OLED Micro‐Displays

Efficient top-emitting phosphorescent green OLED micro-displays were developed using a highly reflective anode patterned over active matrix single crystal silicon. Single emission layer devices were fabricated using high Tg materials with efficiencies ∼80 cd/A, 18% EQE and stable green color coordinates (0.33, 64). Green OLED Micro-display lifetimes were measured.

59.2: High Performance Top Emitting OLED Devices

High performance top-emitting full color organic light-emitting diode (OLED) micro-displays were developed using a highly reflective anode patterned over active matrix single crystal silicon. Dual emission layer white OLED devices were fabricated using high Tg materials with typical efficiencies ∼ 10 cd/A and CIE x and y coordinates of 0.32 and 0.34 respectively. Stable color coordinates over a wide range of video grey levels were obtained from white using color filters. Room temperature operating luminance half-life at 20 mA/cm2 exceeds 6,000 hrs (>25,000 hrs in video mode). The optical characteristics of the devices were simulated using a full vector field calculation.

Technology and design of an active-matrix OLED on crystalline silicon direct-view display for a wristwatch computer

The IBM Research Division and eMagin Corp. jointly have developed a low-power VGA direct view active matrix OLED display, fabricated on a crystalline silicon CMOS chip. The display is incorporated in IBM prototype wristwatch computers running the Linus operating system. IBM designed the silicon chip and eMagin developed the organic stack and performed the back-end-of line processing and packaging. Each pixel is driven by a constant current source controlled by a CMOS RAM cell, and the display receives its data from the processor memory bus. This paper describes the OLED technology and packaging, and outlines the design of the pixel and display electronics and the processor interface. Experimental results are presented.

VGA active-matrix OLED displays having the single polysilicon TFT pixel structure

Organic light emitting diodes are a new flat panel display technology that offers high luminous efficiencies. In this paper, a VGA format polysilicon active matrix organic light emitting diode display will be presented. The display design and pixel structure will be discussed as well as the integration of the polysilicon TFT with the OLED display process. The method used to drive the display will be presented along with the active matrix display performance.

Design and manufacturing of active-matrix organic light-emitting microdisplays on silicon

An organic light-emitting diode (OLED) microdisplay is described. The OLED display has a top-emitting structure integrated on single-crystal active-matrix driver chips and is sealed in a fully hermetic package. All processing and fabrication is done on 8-in. wafers until final dicing and assembly. The basic structure of the displays, the key manufacturing and processing steps, and initial performance of a monochrome green active-matrix OLED device structure are presented. Key advantages of the chosen approach as well as remaining challenges and requirements for improvements are discussed.

Active matrix organic light emitting diode (AMOLED) performance and life test results

The US Army and eMagin Corporation established a Cooperative Research and Development Agreement (CRADA) to characterize the ongoing improvements in the lifetime of OLED displays. This CRADA also called for the evaluation of OLED performance as the need arises, especially when new products are developed or when a previously untested parameter needs to be understood. In 2006, eMagin Corporation developed long-life OLED-XL devices for use in their AMOLED microdisplays for head-worn applications. RDECOM CERDEC NVESD conducted life tests on these displays, finding over 200% lifetime improvement for the OLED-XL devices over the standard OLED displays, publishing results at the 2007 and 2008 SPIE Defense and Security Symposia1,2. In 2008, eMagin Corporation made additional improvements on the lifetime of their displays and developed the first SXGA (1280 × 1024 triad pixels) OLED microdisplay. A summary of the life and performance tests run at CERDEC NVESD will be presented along with a recap of previous data. This should result in a better understanding of the applicability of AMOLEDs in military and commercial head mounted systems: where good fits are made, and where further development might be desirable.

41.3: A Low-Power AMOLED Microdisplay with Ultra-High Pixel Density and Extended Operating Temperature Range

A low-power, full-color AMOLED microdisplay with an ultra-high color pixel density of 2300 ppi and excellent image quality is reported. Based on a new pixel driver scheme, a key feature of the display is its built-in temperature compensation circuitry that achieves instant operation at low temperatures without the need for power-hungry heaters or complex external functionality.