Phosphorescent organic light emitting diodes (PHOLEDs) feature high efficiency, brightness, and color tunability suitable for both display and lighting applications. However, overcoming the short operational lifetime of blue PHOLEDs remains possibly the most challenging problem in the field of organic electronics. Their short lifetimes originate from the annihilation of high energy, long-lived blue triplets that leads to molecular dissociation. Here, we introduce the polariton-enhanced Purcell effect to reduce the triplet density, and hence the probability for destructive high-energy triplet-polaron (TPA) and triplet-triplet annihilation (TTA) events. Besides the common optical modes in conventional devices, we couple triplets to plasmon-exciton-polaritons and cavity modes to significantly increase the strength of the Purcell effect. We achieve a four-fold improvement in LT95 (time to 95% of the initial luminance) of a blue PHOLED with a Purcell factor of 2.4. Furthermore, the chromaticity coordinates of a cyan emitting Ir-complex were shifted to (0.14, 0.14), a deep blue color suitable for displays. The power law between lifetime enhancement and the Purcell factor is between 1.4 and 2.2, suggesting contributions to degradation from both TPA and TTA. The polariton-enhanced Purcell effect and microcavity engineering provide new possibilities for extending the PHOLED lifetime, particularly in the deep blue spectral range essential for wide color gamut displays.
Exciton distribution in white OLEDs (WOLEDs) with broad emission zones containing multiple material interfaces are difficult to accurately predict, making their optimal design accessible only through the fabrication and measurement of numerous iterations involving different materials and layer thicknesses. We present a comprehensive model that is suitable for predicting the exciton distribution in state-of-art WOLEDs. The model captures both charge and exciton dynamics and takes all structural components of complex WOLEDs into consideration, including more than three interface barriers and emission layers with multiple dopants. The model quantitatively reproduces the measured exciton profile and suggests a charge blocking layer reduces the intensity-dependent color shifts in WOLEDs. The emission of WOLEDs with and without blocking layers are measured, and matches the calculated exciton distribution.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.