Researchers from Japan's Kyushu University developed a new technology called singlet fission that enables near-infrared OLED materials to surpass the 100% limit for exciton production - or achieve an internal quantum efficiency (IQE) of over 100%. Singlet fission was already used in OPVs, but this is the first time that it was demonstrated with OLEDs.
Achieving over 100% is possible because at 100% IQE all charges form excitons that emit light. The new technique splits the energy from a high-energy excitons into two low level ones. The new OLED emitter materials use molecules in which singlets can transfer half of their energy to neighboring molecules while keeping half of the energy for themselves - each singlet creates two triplets. The emitters emit near-infrared light.
In their first research, the researchers achieved an IQE of 100.8%. The researchers nope to enhance the materials - up to an IQE of 125%, which is the current limit as OLED emission results in 25% singlets and 75% triplets. The researchers, however, will also look into converting triplets to singlets which could increase the IQE to 200%.