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New route to break the 25% upper limit of internal quantum efficiency of OLEDs: the emission from doublet
May 11, 2015

The triplet harvesting is a main challenge in the field of organic light-emitting devices (OLEDs), due to the spin-forbidden nature of the radiative decay of triplet. Li Feng’s group in our Lab proposed a new kind of OLEDs utilizing the emission from doublet to circumvent the transition problem of triplet for the first time. In this kind of OLEDs, organic open-shell molecules, neutral pi radicals, are used as the emitter. For the open-shell molecule, there is only one unpaired electron in the highest singly occupied molecular orbital (SOMO). When this electron is excited into the lowest singly unoccupied molecular orbital (SUMO), the SOMO is empty. Thus, its transition back to the SOMO is always spin-allowed in despite of its spin state. TTM-1Cz, a kind of photoluminescent radical, was used as the emitter to fabricate the OLEDs. The spin configuration of excited states of TTM-1Cz is verified to be doublet. The results pave a new promising way to obtain 100 % internal quantum efficiency of OLEDs. This work has been published online on 27th April, 2015 as the hot paper of Angew. Chem. Int. Ed. DOI: 10.1002/anie.201500242



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