Strategies for improving the outcoupling efficiency in organic light emitting diodes for lighting and display applications

Y. Li, N. B. Kotadiya, B. van derZee, P. W. M. Blom, G.-J. A. H. Wetzelaer, Optical Outcoupling Efficiency of Organic Light-Emitting Diodes with a Broad Recombination Profile. Adv. Optical Mater. 2021, 9, 2001812. https://doi.org/10.1002/adom.202001812

Researchers have made significant advancements in enhancing the efficiency of organic light-emitting diodes (OLEDs) by addressing two major light loss channels: substrate guided modes and evanescent modes. By micromachining hole patterns with specific characteristics onto the air/glass side of the OLED substrate, they achieved a 60% enhancement in light outcoupling efficiency (ηout) while reducing viewing angle dependence. This innovative approach prevents total internal reflection events and minimizes interference effects, improving OLEDs' general lighting applications.

In addition, a materials engineering approach was used to reduce losses to evanescent modes by employing π-conjugated polymers in the emissive layer. These polymers naturally emit TE-polarized radiation, reducing losses and enhancing ηout. The researchers developed a novel solution withdrawal coating (SWC) technique to simultaneously deposit the polymer film and control uniaxial orientation, resulting in highly efficient OLED displays with linearly polarized luminescence. This groundbreaking work paves the way for further advancements in the OLED technology, making it more efficient and versatile for various applications.

SETFOS was used to simulate the mode contributions within the OLED and optimize the dimensions of the glass patterns made at the air/substrate interface.