Jinouk Song

Area-selective external light extraction for metal bus equipped large area transparent organic light-emitting diodes

Area-selective external light extraction films based on wrinkle structured films were applied to large transparent organic light-emitting diodes (TOLEDs) with auxiliary metal buses. To be specific, on the external surface of the glass, we selectively formed a wrinkle structured film, which was aligned to the auxiliary metal electrodes. The wrinkle-structured film was patterned using a photo-mask and UV curing, which has the same shape of the auxiliary metal electrodes. With this area-selective film, it was possible to enhance the external quantum efficiencies of the bottom and top emissions TOLEDs by 15.7% and 15.1%, respectively, without significant loss in transmittance. Widened angular luminance distributions were also achieved in both emissions directions.

Lensfree OLEDs with over 50% external quantum efficiency via external scattering and horizontally oriented emitters

High efficiency is important for successful deployment of any light sources. Continued efforts have recently made it possible to demonstrate organic light-emitting diodes with efficiency comparable to that of inorganic light-emitting diodes. However, such achievements were possible only with the help of a macroscopic lens or complex internal nanostructures, both of which undermine the key benefits of organic light-emitting diodes as an affordable planar light source. Here we present a systematic way to achieve organic light-emitting diodes with ultrahigh efficiency even only with an external scattering film, one of the simplest low-cost outcoupling structures. Through a global, multivariable analysis, we show that scattering with a high degree of forwardness has a potential to play a critical role in realizing ultimate efficiency. Combined with horizontally oriented emitters, organic light-emitting diodes equipped with particle-embedded films tailored for forward-intensive scattering achieve a maximum external quantum efficiency of 56%.Light extraction approaches based on a macroscopic lens in organic light-emitting diodes (OLEDs) enables competitive performance, but compromise on the technology’s key benefits. Here, the authors demonstrate ultrahigh efficiency OLEDs via a device strategy based on forward light scattering.

Trans-scale optical simulation for OLEDs involving scattering substrates

Scatter-embedded substrate is a powerful platform for improving light extraction efficiency in OLED lighting. In this work, we propose trans-scale optical simulation for OLEDs involving scattering substrates. This simulation combines rigorous dipole model analyzing thin-film stacks with Monte-Carlo simulation based on Henyey-Greenstein phase function for tracing rays encountered with specific size of scatter. The simulation provides a useful tool to analyze and design OLEDs with bulk scatter.