Minimizing round-trip loss for near-unity quantum efficiency in organic light-emitting diodes
Abstract
Modern organic light-emitting diodes (OLEDs) reach internal quantum efficiencies close to 100%, yet in a planar device only 20-30% of photons escape. External outcoupling structures on high-index substrates recover some of the trapped light, but external quantum efficiencies (EQEs) have stalled at 55-60% across different optical designs, and the origin of this ceiling is not fully understood. Here we identify light extraction in such OLEDs as a multi-pass process: light that the outcoupling structure fails to extract returns to the OLED, is reflected back and may escape over multiple passes, with the efficiency governed by the absorption per round trip. Absorption loss is minor in conventional planar OLEDs, but it becomes dominant and accounts for the observed efficiency ceiling when an outcoupling structure is attached. Consistent with this picture, adding a low-loss auxiliary reflector raised the EQE of an OLED on a high-index microlens substrate from 51% to 77% without any change to the OLED stack or the outcoupling structure, the highest value reported for a single-junction OLED without a macroscopic extraction lens; for an OLED on a conventional glass substrate an estimated 92% of the light delivered to the substrate was extracted. We derive four design rules that keep round-trip losses to a few percent and predict that EQEs around 90% are feasible with established materials. Under these rules, microcavity tuning and emitter orientation largely cease to matter, and high efficiency is retained across a wide range of microlens designs and scattering layers.
Related
- Highly efficient hybrid white organic light-emitting diodes with suppressed efficiency roll-off based on dual triplet-management strategy
- Multi-cycle rapid thermal annealing for enhancement of luminescence performance in InGaN/GaN green light-emitting diodes
- Design Principles of High‐Radiance and Stable Perovskite Light‐Emitting Diodes
- Steady-state cooperative emission of interlayer excitons in atomically thin light-emitting diodes
- High-Efficiency Field-Free Superconducting Diodes in Mo2N/FePt Bilayers
BibTeX
@misc{kim2026minimizing,
title = {{Minimizing round-trip loss for near-unity quantum efficiency in organic light-emitting diodes}},
author = {Junho Kim and Seonjeong Lee and Seunghyup Yoo and Malte C. Gather},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.12065},
eprint = {2610.12065},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.12065},
}
RIS
TY - UNPB
TI - Minimizing round-trip loss for near-unity quantum efficiency in organic light-emitting diodes
AU - Junho Kim
AU - Seonjeong Lee
AU - Seunghyup Yoo
AU - Malte C. Gather
PY - 2026
DA - 2026/10/08
PB - arXiv
DO - 10.48550/arxiv.2610.12065
UR - https://arxiv.org/abs/2610.12065
AB - Modern organic light-emitting diodes (OLEDs) reach internal quantum efficiencies close to 100%, yet in a planar device only 20-30% of photons escape. External outcoupling structures on high-index substrates recover some of the trapped light, but external quantum efficiencies (EQEs) have stalled at 55-60% across different optical designs, and the origin of this ceiling is not fully understood. Here we identify light extraction in such OLEDs as a multi-pass process: light that the outcoupling structure fails to extract returns to the OLED, is reflected back and may escape over multiple passes, with the efficiency governed by the absorption per round trip. Absorption loss is minor in conventional planar OLEDs, but it becomes dominant and accounts for the observed efficiency ceiling when an outcoupling structure is attached. Consistent with this picture, adding a low-loss auxiliary reflector raised the EQE of an OLED on a high-index microlens substrate from 51% to 77% without any change to the OLED stack or the outcoupling structure, the highest value reported for a single-junction OLED without a macroscopic extraction lens; for an OLED on a conventional glass substrate an estimated 92% of the light delivered to the substrate was extracted. We derive four design rules that keep round-trip losses to a few percent and predict that EQEs around 90% are feasible with established materials. Under these rules, microcavity tuning and emitter orientation largely cease to matter, and high efficiency is retained across a wide range of microlens designs and scattering layers.
ER -