51.1: Invited Paper: Optical Design of Enhanced Light Extraction Efficiency in Multi‐Stacked OLEDs Coupled with High Refractive‐Index Medium and Back‐Cavity Structure

The light extraction of OLED has been successfully enhanced by employing high refractive index intermediate layer in the anode side and back-cavity structure in the cathode side Back-cavity structure consisting of semi-transparent cathode, optical buffer layer and high reflection mirror was newly introduced to reduce surface plasmon loss in the metal cathode. The high index inter-layer plays the role in the energy transfer from the waveguide mode to the substrate propagation mode by refractive matching between high refractive index ITO anode and the normal index glass substrate. From the results of detail optical calculation based on the multi-scale analysis including near-field optics, approximately 70∼80% of electromagnetic energy in the dipole emission was effectively converted to the glass and air modes by suppressing both surface plasmon and waveguide losses. The phosphorescent green light emitting device exhibits higher light extraction by a factor of 1.6∼1.7.