Phosphorescent White OLEDs for Solid-state Lighting
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1212-S02-01
Phosphorescent White OLEDs for Solid-State Lighting Sean Xia, Peter Levermore, Vadim Adamovich, Chun Lin, Ray C. Kwong, Michael S. Weaver, Julie J. Brown Universal Display Corporation, 375 Phillips Blvd. Ewing, NJ 08618, U.S.A. ABSTRACT White OLEDs (WOLEDTMs) fabricated using energy efficient phosphorescent OLED (PHOLEDTM) technology open up exciting new ways to develop efficient white lighting. WOLEDs have the potential to transform the lighting industry. In this presentation, phosphorescent WOLEDs with high conductivity transport layers will be discussed. White light can be generated by partial energy transfer from blue to green and red. Single WOLED stacks are demonstrated that match the Energy Star® lighting color criteria for 2700K and 3000K with high efficiency (~80 lm/W) and high color rendering indices (~80). Both devices had operational lifetimes (LT70%) over 30,000 hours measured from an initial luminance of 1,000 cd/m2. Different techniques to improve optical outcoupling will also be discussed. INTRODUCTION Lighting consumes around 765 TWh of electricity each year in the United States, or nearly 30% of all electricity produced for buildings, which corresponds to 18% of total building energy consumption. In terms of total primary energy consumption, lighting accounts for 8.3% of all the energy used in the United States, or about 22% of all the electricity produced. Nearly half of current lamp sales by volume are inefficient incandescent light bulbs, which have a total power efficacy (PE) of 12-17 lm/W. Switching to efficient lighting systems would trim the global electricity bill and save energy significantly. White organic light-emitting device (WOLED) technology has been considered as a promising candidate for next generation solid state lighting (SSL) due to its intriguing properties [1-3]. WOLEDs are large area diffuse light sources that are thin, flat, lightweight, and environmental friendly. They have fast response time and are fully dimmable. Steady progress has been made during the last few years in terms of efficiency, lifetime, and color. In 2008, we have achieved highly efficient WOLEDs with PE over 100 lm/W at 1000 cd/m2 using phosphorescent emitters [4]. Phosphorescent OLEDs (PHOLEDs) use both singlet and triplet excited states to emit light, which can theoretically achieve 100% internal quantum efficiency (IQE) [5]. PHOLEDs with three primary colors have shown external quantum efficiency (EQE) over 20%. Considering the optical effects such as outcoupling, the IQE of such devices is close to 100%. Several approaches have been taken to achieve WOLEDs such as single emissive layer with multiple doping [6], multiple emissive layers with different emitters in different layers [3], and stacking of a number of single color OLEDs (SOLED®s) [8]. Among these approaches, SOLED structures have recently gained a lot of popularity due to their ability to incorporate both fluorescent and phosphorescent emitters, realize long lifetime by driving the device at low current, and generating a high c
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