TY - JOUR
T1 - Fast spin-flip enables efficient and stable organic electroluminescence from charge-transfer states
AU - Cui, Lin-Song
AU - Gillett, Alexander J.
AU - Zhang, Shou-Feng
AU - Ye, Hao
AU - Liu, Yuan
AU - Chen, Xian-Kai
AU - Lin, Ze-Sen
AU - Evans, Emrys W.
AU - Myers, William K.
AU - Ronson, Tanya K.
AU - Nakanotani, Hajime
AU - Reineke, Sebastian
AU - Bredas, Jean-Luc
AU - Adachi, Chihaya
AU - Friend, Richard H.
PY - 2020/10
Y1 - 2020/10
N2 - A spin-flip from a triplet to a singlet excited state, that is, reverse intersystem crossing (RISC), is an attractive route for improving light emission in organic light-emitting diodes, as shown by devices using thermally activated delayed fluorescence (TADF). However, device stability and efficiency roll-off remain challenging issues that originate from a slow RISC rate (kRISC). Here, we report a TADF molecule with multiple donor units that form charge-resonance-type hybrid triplet states leading to a small singlet–triplet energy splitting, large spin–orbit couplings, and a dense manifold of triplet states energetically close to the singlets. The kRISC in our TADF molecule is as fast as 1.5 × 107 s−1, a value some two orders of magnitude higher than typical TADF emitters. Organic light-emitting diodes based on this molecule exhibit good stability (estimated T90 about 600 h for 1,000 cd m−2), high maximum external quantum efficiency ('29.3%) and low efficiency roll-off ('2.3% at 1,000 cd m−2).
AB - A spin-flip from a triplet to a singlet excited state, that is, reverse intersystem crossing (RISC), is an attractive route for improving light emission in organic light-emitting diodes, as shown by devices using thermally activated delayed fluorescence (TADF). However, device stability and efficiency roll-off remain challenging issues that originate from a slow RISC rate (kRISC). Here, we report a TADF molecule with multiple donor units that form charge-resonance-type hybrid triplet states leading to a small singlet–triplet energy splitting, large spin–orbit couplings, and a dense manifold of triplet states energetically close to the singlets. The kRISC in our TADF molecule is as fast as 1.5 × 107 s−1, a value some two orders of magnitude higher than typical TADF emitters. Organic light-emitting diodes based on this molecule exhibit good stability (estimated T90 about 600 h for 1,000 cd m−2), high maximum external quantum efficiency ('29.3%) and low efficiency roll-off ('2.3% at 1,000 cd m−2).
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U2 - 10.1038/s41566-020-0668-z
DO - 10.1038/s41566-020-0668-z
M3 - RGC 21 - Publication in refereed journal
SN - 1749-4885
VL - 14
SP - 636
EP - 642
JO - Nature Photonics
JF - Nature Photonics
IS - 10
ER -