Thermal Management of Phosphorescent Organic Light Emitting Devices

Novel high-efficiency solid-state light sources are needed to help reduce the ever increasing demand for energy. Organic Light Emitting Devices (OLED), which are energy efficient diffuse light sources that may compete most directly with and offer a green energy saving alternative to conventional incandescent light sources. However, lifetime of large-area OLED lighting panels is still one of the biggest technical challenges, where studies have shown operation temperature has strong impact on device lifetime. It is therefore very important to improve the thermal management for large-area OLED lighting to extend panel lifetimes. This Phase II work proposes to continue the improvement of thermal management for large-area OLED light panels, based on the success of our Phase I program. We will develop various approaches to improve the thermal management including building physical model, establishing panel-level testing methods, optimizing panel design, and exploring novel substrates and encapsulation systems. During Phase I, we successfully demonstrated high efficacy 15 cm x 15 cm white PHOLED lighting panels achieving high efficacy of 66 lm/W at 2,600 lm/m2 (1,000 cd/m2) with a lifetime of 30,000 hours. We characterized the temperature dependence of our PHOLEDs and our study shows the importance of reducing the operation temperature to improve device lifetime. IR images of lighting panels were analyzed and the results provide guidelines for designing panels with improved thermal management . During our proposed Phase II program, we intend to further broaden our studies of thermal behavior of OLED devices, and to develop various technologies to improve the thermal management for large-area OLED panels. The key Phase II deliverable is a 15 cm 15 cm WOLED panel with low operating temperature & lt; 30 C, power efficacy & gt; 65 lm/W, CRI & gt; 80, CCT & amp; CIE (x, y) meeting Energy Star Criteria for Solid State Lighting at a high light output of 10,000 lm/m2 (4,000 cd/m2). This power efficacy target is equivalent to 85 lm/W at 2,500 lm/m2 (1,000 cd/m2). The low-temperature operation will enable 50% improvement on panel lifetime to LT70 & gt; 10,000 hrs at 10,000 lm/m2. Commercial Applications and Other Benefits: Today, OLED technology is the leading emerging technology for flat panel displays (FPDs), with recent product introductions in cell phones. Many of these features that are desired for FPDs are also making OLED technology of great interest to the solid-state lighting community. For example, OLEDs are bright and colorful lambertian emitters with excellent power efficiency at low voltages. In addition, OLEDs are thin-film devices that provide thin form factors especially when built on flexible substrates.