Stress Testing of Organic Light- Emitting Diode Panels and Luminaires

Abstract

Luminaires and other lighting devices using organic light-emitting diode (OLED) sources have many advantages over their competitors for indoor lighting, including thin form factors that produce highly diffuse, potentially low-glare, lighting with excellent color rendering properties. However, several significant issues with OLED products have limited their commercial acceptance to date, including source efficacy, source lifetime, driver performance, and initial costs. The U.S. Department of Energy (DOE) has released four reports on OLED technologies to provide the lighting industry with information on the state of the technology. These reports include the evaluation of two different field deployment sites, a market analysis, and an independent assessment of the performance of several commercially available OLED products. This report builds on previous DOE efforts with OLED technology by updating information on a previously benchmarked OLED product (the Chalina luminaire from Acuity Brands) and provides new benchmarks on the performance of Brite 2 and Brite Amber OLED panels from OLEDWorks. During the tests described here, samples of these devices were subjected to continuous operation in stress tests at elevated ambient temperature environments of 35°C or 45°C. In addition, samples were also operated continuously at room temperature in a room temperature operational life test (RTOL). One goal of this study was to investigate whether these test conditions can accelerate failure of OLED panels, either through panel shorting or an open circuit in the panel. These stress tests are shown to provide meaningful acceleration of OLED failure modes, and an acceleration factor of 2.6 was calculated at 45°C for some test conditions. In addition, changes in the photometric properties of the emitted light (e.g., luminous flux and chromaticity maintenance) was also evaluated for insights into the long-term stability of these products compared to earlier generations. Because OLEDs are a lighting system, electrical testing was also performed on the panel-driver pairs to provide insights into the impact of the driver on long-term panel performance. The Chalina luminaire from Acuity Brands uses OLED panels made by LG Display. These panels utilize a 3tandem stack structure with one layer containing a blue fluorescent emitter and two layers containing combined green and red phosphorescent emitters. In this study, three different generations (denoted as Gen 1, Gen 2, and Gen 3) of OLED panels were found to be used in the tested Chalina luminaires. Gen 2 and Gen 3 OLED panels are characterized by a copper foil adhered to the back of the panel, whereas Gen 1 OLED panels have a mirror-like finish on the back. Chalina luminaires with Gen 1 panels were previously discussed in CALiPER 24.

Round 2 Update of Stress Testing Results for Organic Light-Emitting Diode Panels and Luminaires

“…The U.S. Department of Energy (DOE) has released five reports about OLED technologies to provide information and analysis to the lighting industry [1]. These reports include the evaluation of two different field deployment sites, a market analysis, and two independent assessments of the performance of select commercially available OLED products [2].…”

“…However, testing standards for OLED lighting products will likely need to comply with the existing testing infrastructure for LED lighting, which relies on environmental stresses of temperature, vibration, and rapid power cycling. Current research about OLED testing methods point to the use of mildly elevated ambient temperatures (e.g., 35°C to 65°C) as being appropriate for accelerated stress tests (ASTs) [2,8,9].…”

“…The U.S. Department of Energy (DOE) continues to support the development of OLED technologies as an integral part of the solid-state lighting (SSL) program [6]. DOE has published five reports that highlight commercial OLED technologies: two field evaluations [10,11], a Commercially Available LED Product Evaluation and Reporting (CALiPER) study [12], initial results from ASTs of OLED panels and luminaires [2], and a market analysis [13]. A general conclusion from these studies is that the cosine emission profile of the light produced by OLED devices is beneficial for indoor lighting applications and provides OLEDs with a unique look and functionality compared with the generally directional nature of inorganic LED lighting.…”

“…Although panels from both manufacturers use fluorescent blue-emitting organic molecules and phosphorescent red-and green-emitting organic molecules, panels from LG Display employ a three-tandem stack device structure [14], whereas panels from OLEDWorks incorporate a six-tandem stack structure [15]. Panels from LG Display have been used in a broad range of luminaire types examined in DOE studies, including both Gateway and CALiPER reports [2,[10][11][12][13]. The luminaires in these DOE reports that incorporated panels from OLEDWorks mainly used the older Brite 1 technology [10][11][12], although the newer Brite 2 panels were examined in the most recent DOE reports [2,12].…”

“…Panels from LG Display have been used in a broad range of luminaire types examined in DOE studies, including both Gateway and CALiPER reports [2,[10][11][12][13]. The luminaires in these DOE reports that incorporated panels from OLEDWorks mainly used the older Brite 1 technology [10][11][12], although the newer Brite 2 panels were examined in the most recent DOE reports [2,12]. Recently, OLEDWorks introduced a new generation of OLED panels, the Brite 3, which provides enhanced capabilities over previous products [16].…”