Abstract
Circularly polarized (CP) light is of interest in areas such as quantum optical computing, optical spintronics, biomedicine, and high efficiency displays. Direct emission of CP light from organic light-emitting diodes (OLEDs) has been a focus of research as it has the immediate application of increasing efficiency and simplifying device architecture in OLED based displays. High dissymmetry (gEL) factor values have been reported for devices employing fluorescent polymers, but these CP-OLEDs are limited in their ultimate efficiencies by the type of emissive electronic transitions involved. In contrast, phosphorescent OLEDs (PHOLEDs) can emit light from triplet excited states and can therefore achieve very high efficiencies. However, CP-PHOLEDs are significantly understudied, and the two previous reports suffered from very low brightness or gEL values. Here, we use a platinahelicene complex to construct a CP-PHOLED that achieves both a display level brightness and a high gEL factor. The dissymmetry of CP emission reached with this proof-of-concept single-layer helicene-based device is sufficient to provide real-world benefits over nonpolarized emission and paves the way toward chiral metal complex-based CP-PHOLED displays.
Highlights
That achieves both a display level brightness and a high gEL factor
The dissymmetry of Circularly polarized (CP) emission reached with this proof-of-concept single-layer helicene-based device is sufficient to provide real-world benefits over nonpolarized emission and paves the way toward chiral metal complexbased CP-phosphorescent OLEDs (PHOLEDs) displays
The maximum dissymmetry factor |gEL| of 0.38 reported here is sufficient to afford a 19% increased brightness compared to nonpolarized organic light-emitting diodes (OLEDs) of comparable efficiency in a display using a common circular polarization antiglare filter
Summary
A g factor of zero corresponds to light with no circular polarization, while +2 and −2 correspond to fully left- or right-handed CP light, respectively. The maximum dissymmetry factor |gEL| of 0.38 reported here is sufficient to afford a 19% increased brightness compared to nonpolarized OLEDs of comparable efficiency in a display using a common circular polarization antiglare filter Until 2013, most examples[13] were based on the use of Figure 1. Polymers and oligomers bearing chiral side chains.[14] OLEDs based on these chiral organic semiconducting materials can reach impressive |gEL| factors of up to 0.35,15 but their usage often involves complicated device fabrication (such as the use of alignment layers). Our group employed an operationally simpler approach, whereby a nonemissive, chiral helicene[16,17] dopant was blended with a standard nonchiral polyfluorene-based polymer, which induced CP electroluminescence from the polymer with a |gEL| factor of 0.2.18,19. Fluorescent materials, like the emissive polymers described above, cannot emit light from triplet states and are limited to a maximum of 25% internal quantum efficiency from consideration of exciton spin statistics.[20,21] Phosphorescent materials, can emit light from triplet states (phosphorescence) and can be used to fabricate much more efficient phosphorescent OLEDs (PHOLEDs)[22−24] that achieve internal quantum efficiencies of nearly 100%25 and external quantum efficiencies of 30%.26 The desired phosphor-
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
