organic light-emitting diode

organic light-emitting diode
Name	Organic light-emitting diode
Invented	1987
Inventors	Ching W. Tang, Steven Van Slyke
Type	Electroluminescent device
Used for	Displays, lighting

organic light-emitting diode

Organic light-emitting diode devices are thin-film electroluminescent devices that emit light from organic compounds when electrically biased, combining ideas from Thomas Edison's work on light sources, Heinrich Hertz's studies of electromagnetism, Alexander Graham Bell's telecommunications innovations, 1940s vacuum-tube displays, and later semiconductor developments at Bell Labs and IBM. They form the basis of modern displays influenced by standards and markets shaped by Sony Corporation, Samsung Electronics, LG Corporation, Apple Inc., Google LLC, and Microsoft Corporation, and are central to research at institutions such as Massachusetts Institute of Technology, Stanford University, University of Cambridge, University of Oxford, and Tsinghua University.

Introduction

OLED technology emerged as a marriage of organic chemistry and solid-state physics in contexts that include research laboratories at Eastman Kodak Company and industrial research groups at DuPont and Philips. The devices are contrasted with inorganic technologies promoted by Intel Corporation, Texas Instruments, and NVIDIA Corporation and relate to display ecosystems driven by standards from International Electrotechnical Commission, Society of Motion Picture and Television Engineers, and marketplace forces involving Walmart Inc.. OLED adoption has been accelerated by consumer brands such as LG Electronics, Samsung Display, Panasonic Corporation, Sony, and Huawei Technologies.

History and development

Early observations of electroluminescence trace to work at Rutgers University and laboratories connected to General Electric and RCA Corporation, leading to breakthroughs at Eastman Kodak where Ching W. Tang and Steven Van Slyke demonstrated efficient double-layer devices in 1987. Subsequent milestones include developments by research groups at Cambridge University (including Richard Friend), patents contested among Phillips Research, Koninklijke Philips N.V., DuPont, and corporate commercialization by Nokia Corporation and Motorola. Government funding from agencies such as the National Science Foundation, European Research Council, and Japan Science and Technology Agency supported academic work at Harvard University, Yale University, University of California, Berkeley, and University of Tokyo.

Structure and operating principles

OLEDs consist of stacked thin films including electrodes, charge injection layers, transport layers, emissive organic layers, and encapsulation, akin to layered devices developed at Bell Labs and later optimized at Eastman Kodak and Sony. Operation relies on charge injection, transport, exciton formation, and radiative recombination, influenced by concepts from Albert Einstein's work on stimulated and spontaneous emission and semiconductor physics advanced at Bell Labs and Princeton University. Device modeling and simulation have been advanced through collaborations with Lawrence Berkeley National Laboratory, Argonne National Laboratory, and Sandia National Laboratories.

Materials and types

Organic emissive materials include small molecules pioneered by Ching W. Tang and polymers advanced by researchers such as Alan J. Heeger, Alan G. MacDiarmid, and Hideki Shirakawa whose conductive polymer work influenced OLED polymers. Phosphorescent emitters using heavy metals were developed building on coordination chemistry at institutions like California Institute of Technology and ETH Zurich. Device types include small-molecule OLEDs, polymer OLEDs (PLEDs), vacuum-deposited OLEDs, solution-processed devices, phosphorescent OLEDs, thermally activated delayed fluorescence OLEDs, and stacked or tandem OLEDs, developed in labs at Kyoto University, Seoul National University, Tsinghua University, and Imperial College London.

Device fabrication and manufacturing

Manufacturing approaches range from vacuum thermal evaporation used by Canon Inc. and Seiko Epson to inkjet printing and roll-to-roll processing explored by Universal Display Corporation partners and startups incubated by Silicon Valley accelerators. Fabrication involves cleanroom facilities similar to those at Intel Corporation fabs and pilot lines established by LG Display and Samsung Display. Encapsulation technologies and barrier films draw on materials science research from 3M Company and DuPont to protect devices from moisture and oxygen.

Performance characteristics and metrics

Key metrics include luminance, external quantum efficiency, internal quantum efficiency, power efficacy, color gamut standards tied to Rec. 709 and Rec. 2020, lifetime (T50, T95), and operational stability evaluated by testing protocols from Underwriters Laboratories and Institute of Electrical and Electronics Engineers. Color coordinates and perceptual metrics relate to work by Commission Internationale de l'Éclairage and imaging standards used in devices from Apple Inc. and Sony.

Applications and commercial products

OLEDs power displays in smartphones from Apple Inc., Samsung Electronics, and Google, televisions marketed by LG Electronics, wearables from Fitbit, automotive dashboards designed by Bosch, and lighting fixtures developed by Philips Lighting and Osram. Specialty uses include virtual reality headsets supported by Oculus VR and HTC Corporation, transparent displays prototyped by Microsoft Corporation and Nissan Motor Corporation, and flexible devices demonstrated by Royole Corporation and startups supported by Y Combinator.

Challenges and future directions

Remaining challenges include blue emitter lifetime driven by molecular stability studied at Max Planck Society and Riken, manufacturability scaling similar to transitions faced by Semiconductor Research Corporation, cost pressures affected by supply chains involving Foxconn Technology Group and TSMC, and sustainability concerns addressed by lifecycle analyses at World Resources Institute and United Nations Environment Programme. Future directions include integration with microLED research at Epistar Corporation, hybrid displays from collaborations between Sony and Samsung, advances in materials chemistry from groups led by Ben Feringa and Jean-Marie Lehn, and policy and standards coordination by International Telecommunication Union and International Organization for Standardization.

Category:Display technology