Exciplex emissions derived from exceptionally long-distance donor and acceptor molecules.

Intermolecular electron-hole coupling in organic semiconductor excited states plays important roles in organic light-emitting diodes and organic photovoltaics, and the distance of the coupling is typically only on the order of a few nanometers. Here, we report exceptionally long-distance coupled exciplex emissions between electron-donor and electron-acceptor molecules even with a 70 nm-thick spacer layer. Donor/spacer (∼70 nm)/acceptor-type stacked films showed a low-energy band emission, which is not ascribed to the emission of the donor, spacer, and acceptor themselves, but well corresponds to the energy difference between the highest occupied molecular orbital of the donor and the lowest unoccupied molecular orbital of the acceptor. Delayed transient photoluminescence (PL) and electroluminescence (EL) decays and PL quenching by oxygen at the low-energy band were observed and are consistent with the characteristics of the exciplex species.

High-Performance Green OLEDs Using Thermally Activated Delayed Fluorescence with a Power Efficiency of over 100 lm W(-1).

A green organic light-emitting device (OLED) with an extremely high power efficiency of over 100 lm W(-1) is realized through energy transfer from an exciplex. An optimized OLED showed a maximum external efficiency of 25.7%, and a power efficiency of 79.4 lm W(-1) at 1000 cd m(-2) , which is 1.6-times higher than that of state-of-the-art green thermally activated delayed fluorescence (TADF) OLEDs.

Blue thermally activated delayed fluorescence materials based on bis(phenylsulfonyl)benzene derivatives.

Two blue thermally activated delayed fluorescence molecules based on bis(phenylsulfonyl)benzene with very small singlet-triplet splitting energy were designed and synthesized by combining 3,6-di-tert-butylcarbazole with 1,4-bis(phenylsulfonyl)benzene and 1,3-bis(phenylsulfonyl)benzene, and a maximum external quantum efficiency of 11.7% was achieved for an electroluminescent device.

High-performance blue phosphorescent OLEDs using energy transfer from exciplex.

An efficient energy transfer from an exciplex between a sulfone and an arylamine derivatives to a blue phosphorescent emitter enables OLED performances among the best, of over 50 lm W(-1) at 100 cd m(-2) . The formation of the exciplex realizes a barrier-free hole-electron recombination pathway, thereby leading to high OLED performances with an extremely low driving voltage of 2.9 V at 100 cd m(-2) .