Reaching 100% Efficient OLEDs
Converting Triplet Excitons Into Singlet States Without Spin Orbit Coupling
Prof. Dr. Andy Monkman – Organic Electroactive Materials Research Group – Department of Physics, Durham University, England
Organic light emitting diodes are now a common place technology, but increasing their internal efficiency to near 100% is difficult.
The main reason for this is that on charge recombination, 75% of excited states formed have triplet character and are non emissive.
At present iridium containing phosphors are used to harvest these states to produced light, but a new type of emitter has been developed that can also convert triplet to singlet states but without the need for a heavy metal or spin orbit coupling, Thermally Activated Delay Fluorescence; ‘TADF’.
In his talk, Monkman will describe the mechanisms that drive TADF and show how molecular design and careful energy level tuning give rise to 22% external quantum efficiency deep blue OLEDs. Throughout, new time resolved photophysical measurements will be explained and used to elucidate the physics behind TADF.
