of oleds

Early Development

Although OLEDs are often viewed as being a modern technology, their development is based on pioneering work dating back to the 1950-60's.

Electrically stimulated emission of light, referred to as electroluminesncence (EL), was first reported in 1953 by A. Bernanose, M. Comte, and P. Vonaux [J. Chim. Phys. 50, 64 (1953)], using a high-voltage AC electrical field. M. Pope et al. at New York University conducted numerous studies on organic EL throughout the 1960’s and reported the first example of DC driven organic EL in 1963 [J. Chem. Phys. 38, 2042 (1963)].

Two years later in 1965 the first organic EL device based on carrier recombination—the same operating mechanism used in all modern LEDs and OLEDs—was reported by W. Helfrich and W.G. Schneider at the National Research Council of Canada [Phys. Rev. Lett. 14, 229 (1965) ]. Numerous patents pertaining to organic EL were also filed in the same time period, with the first patent being filed in 1960 by The Dow Chemical Company [US 3,172,862].

In these early days primitive sample preparation techniques, poor quality electrode contacts, and the low purity of the organic materials used were largely responsible for the inferior performance of early devices and the high operting voltages required (typically 100’s of volts to >1000 V in some cases).

The First OLED

Significant advances in organic EL were made throught the late 1970's and early 80's, due largely in part to improvements in vacuum processing techniques adopted from the microelecrtonics industry and improved purification methods for organic dye molecules developed for Xerography, resulting in devices with dramatically lower operating voltages.

These efforts culminated in 1987 with the first two-layer diode based organic EL device—in other words the first modern OLED—reported by C.W. Tang and S. Van Slyke at Eastman-Kodak [Appl. Phys. Lett. 51, 913 (1987)]. With an operating voltage below 10 V, high brightness of >1,000 cd/m2 (about the same brightness as a modern flat-panel TV), and an efficiency of about 1% the first OLED brought organic EL into the realm of commercial viability for the first time.

Virtually all modern OLEDs are based on the design of the original Eastman-Kodak device.

Recent Developments

More recent developments have been driven by the need for saturated red, green, and blue emission colors as well as higher efficiencies and longer operating lifetimes for OLED displays and lighting.

The first report of a white OLED was made by J. Kido et al. in 1995 [Science 267, 1332 (1995) ], although Eastman-Kodak actually filed a patent in 1993 for a similar white emitting device using a combination of red and blue emitting organic dyes [US 5,059,862].

Another significant milestone was the development of OLEDs utilizing phosporescent emitters, which was first reported by M. Baldo et al. in 1998 [Nature 395, 151 (1998)], although U.S Philips Corporation filed a patent for a phosporescence-based OLED several years earlier in 1994 [US 5,756,224], and Moltech Corporation also filed a patent for an OLED incorporating a phosphorescent organometallic complex in 1989 [US 5,128,587].

OLED Products

Despite the rapid pace of progress in OLED research and development throughtout the late 1980's and early 90's it wasn't until the late 90's that commercial OLED products started to reach the market. In 1997 Pioneer Corporation released the first commercial OLED product, a passive matrix OLED (PMOLED) display for car audio displays.

A decade later in 2007 Samsung Mobile Display released the first commercial active matrix OLED (AMOLED) display. AMOLED is now the technology currently used in virtually all OLED displays found in portable electronics and larger area flat-panel displays.

Although various prototypes of white OLEDs for lighting had been demonstrated over the years, it wasn't until 2010 that OSRAM Opto Semiconductor released the first commerical white OLED lighting panel.