Setting up the new efficiency limit of OLEDs
Speaker: Prof. Jang-Joo Kim, Seoul National University
Department: Electrical Engineering
Location: Engineering Quadrangle B205
Date/Time: Monday, August 11, 2014, 4:00 p.m. - 5:00 p.m.
Abstract: Maximum external quantum efficiency of OLEDs is known to be about 25~30% without any extra light extraction layer if emitting dipoles are randomly oriented. However, an emitter with a horizontal transition dipole moment (TDM) can result in much higher outcoupling efficiency than the vertically aligned dipole as demonstrated in polymers and vacuum evaporated organic molecules. In this talk we will present highly efficient OLEDs using various exciplex forming co-hosts and phosphorescent and fluorescent dyes with horizontally oriented TDM and high PLQY, including blue (EQE of 30%), green (EQE of 32% ), orange (EQE of 32%) and red (EQE of 36%), white (EQE of 28.8%) and fluorescent green (EQE of 30%) OLEDs. The theoretical prediction based on the classical dipole model agrees very well with the experimental data, validating the optical model used for the prediction of the EQEs. Based on the validation, we offer a universal plot of maximum efficiency of OLEDs achievable with different values of PLQY and orientation of TDM without fabricating devices. The optical analysis indicates that OLEDs with EQE higher than 40% can be realized without any extra light extraction layers, if phosphorescent dyes with PLQY and horizontal portion of TDM over 95% are used.
1987 Ph.D., Stanford University (USA)
1980 M.S., Seoul National University (Korea)
1977 B.S., Seoul National University (Korea)
2003.07 ~ present Professor, Seoul National University (Korea)
1996.01 ~ 2003.06 Professor, Gwangju Institute of Science and Technology (Korea)
1987.08 ~ 1995.12 Principal Member of Technical Staff, ETRI (Korea)
1986. 03 ~ 1987.08 Postdoctoral researcher, SRI International (USA)
Organic Optoelectronics, Physics of Organic Semiconductors, Flexible electronics
Prof. Barry Rand