New OLEDs chemistry has tunable chirality for brighter output

July 05, 2019 //By Julien Happich
OLEDs chemistry
Researchers from the Departments of Physics and Chemistry at Imperial College have managed to control the chemistry of OLED materials so as to control the chirality of the light emitting polymers, hence controlling the polarization of the light output.

Presenting their findings in a paper titled ‘Inverting the Handedness of Circularly Polarized Luminescence from Light-Emitting Polymers Using Film Thickness’ published in ACS Nano, the researchers report that blending achiral polymers with chiral small-molecule additives in the new polymer OLEDs chemistry allowed them to control the handedness/sign of the circularly polarized light through absolute stereochemistry. Another interesting finding is that tuning the circularly polarized light output was performed as a function of the active layer thickness, for a fixed optical isomer of the chiral additive.

Changing the handedness of circularly polarized light
through varying the OLED active layer thickness.

The paper reports bright circularly polarized polymer OLEDs (CP-PLEDs) capable of delivering 8000 cd/m2 with an efficiency of 4.0 cd/A and a high dissymmetry of emission of both left-handed (LH) and right-handed (RH) light, depending on the emitter’s thickness. In their experiments and using the same additive, varying the film thickness from 110nm to 160nm was enough to switch the handedness of the polarized light.

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