History of OLED Lights

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Sepia Fireside

Published on April 04, 2012 with No Comments

OLED lights have been around for less than 100 years. The first observations of electroluminescence in organic materials happened in the 1950s. The discovery was made by A. Bernanose and co-workers at the Nancy-Université in France. They experimented with high voltage AC field in the air to material such as acridine orange. The light happened when the materials were dissolved in or deposited on cellulose or thin films of cellophane.

The development of the basis of modern OLED lights and devices happened in 1960. Martin Pope and co-workers at New York Universeity developed ohmic dark-injecting electrode contact to organic crystals. They also found the work functions for contacts. They saw the first DC electroluminescence in 1963.

By 1965, Pope’s group had more advanced observations regarding the absence of an external electric field and conductivity. Using a single anthracene crystal, another group produced double injection recombination electroluminescene in 1965. This forerunner of modern double injection devices was discovered by W. Helfrich and W.G. Schneider of the National Research Council in Canada.

Also in 1965, Dow Chemical researched patented a way of preparing electroluminescent cells using high voltage, AC-driven, electrically-insulated thin layers of melted phosphor. They were made of ground anthracene powder, graphic powder and tetracene.

The device performed was limited by poor electrical conductivity of the organic materials. With the discovery and development of highly conductive polymers, this restriction was overcome. Roger Partridge at the National Physical Laboratory in the U.K. First observed electroluminescence from polymer films with a related patent in 1975 that was published in 1983.

In 1987, the first diode device was reported at Eastman Kodak. Reported by Steven Van Slyke and Ching W. Tang, the device used a two-layer structure with electron transporting and hole transporting layers. The recombination and light emission happened in the middle of the organic layer. Voltage was reduced and improved efficiency led to the modern era of OLED research, OLED lights and OLED production.

In 1990, J.H. Burroughes at Cavendish Laboratory in Cambridge reported a high efficiency green light emitting polymer device that used poly films that were 100 nm thick. Modern OLED lights are less than 500 nm, making them extremely thin.

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