Enhancement of Light Extraction from Waveguide Mode by High Refractive Index Intermediate Layer in Organic Light Emitting Device with Back-Cavity

摘要

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. 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. Back-cavity structure consisting of semi-transparent cathode, optical buffer layer and high reflection mirror was newly introduced to reduce surface plasmon-polariton loss in the metal cathode. From the results of detail optical calculation based on the wave optics considering near-field behavior, approximately 80% of electromagnetic energy in the dipole moment was effectively shifted to the glass and air modes. The phosphorescent green light emitting device exhibits higher light extraction from the waveguide mode by a factor of 1.6.