Quantitative Analysis of the Efficiency of OLEDs.
We present a comprehensive model for the quantitative analysis of factors influencing the efficiency of organic light-emitting diodes (OLEDs) as a function of the current density. The model takes into account the contribution made by the charge carrier imbalance, quenching processes, and optical design loss of the device arising from various optical effects including the cavity structure, location and profile of the excitons, effective radiative quantum efficiency, and out-coupling efficiency. Quantitative analysis of the efficiency can be performed with an optical simulation using material parameters and experimental measurements of the exciton profile in the emission layer and the lifetime of the exciton as a function of the current density. This method was applied to three phosphorescent OLEDs based on a single host, mixed host, and exciplex-forming cohost. The three factors (charge carrier imbalance, quenching processes, and optical design loss) were influential in different ways, depending on the device. The proposed model can potentially be used to optimize OLED configurations on the basis of an analysis of the underlying physical processes.
WCU Hybrid Materials Program, Department of Materials Science and Engineering, Seoul National University , Seoul 151-744, South Korea.
Bomi
B
Sim
Department of Materials Science and Engineering, Seoul National University , Seoul 151-744, South Korea.
Chang-Ki
CK
Moon
Department of Materials Science and Engineering, Seoul National University , Seoul 151-744, South Korea.
Kwon-Hyeon
KH
Kim
WCU Hybrid Materials Program, Department of Materials Science and Engineering, Seoul National University , Seoul 151-744, South Korea.|Department of Materials Science and Engineering, Seoul National University , Seoul 151-744, South Korea.|Research Institute of Advanced Materials (RIAM), Seoul National University , Seoul 151-744, South Korea.
Jang-Joo
JJ
Kim
EQE analysis; charge balance factor; exciton profile; optical design loss; quenching factor