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High-performance light-emitting diodes based on carbene-metal-amides

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Romanov, AS 
Yang, L 
Richter, JM 
Rivett, JPH 


Organic light-emitting diodes (OLEDs) promise highly efficient lighting and display technologies. We introduce a new class of linear donor-bridge-acceptor light-emitting molecules, which enable solution-processed OLEDs with near-100% internal quantum efficiency at high brightness. Key to this performance is their rapid and efficient utilization of triplet states. Using time-resolved spectroscopy, we establish that luminescence via triplets occurs within 350 nanoseconds at ambient temperature, after reverse intersystem crossing to singlets. We find that molecular geometries exist at which the singlet-triplet energy gap (exchange energy) is close to zero, so that rapid interconversion is possible. Calculations indicate that exchange energy is tuned by relative rotation of the donor and acceptor moieties about the bridge. Unlike other systems with low exchange energy, substantial oscillator strength is sustained at the singlet-triplet degeneracy point.



cond-mat.mtrl-sci, cond-mat.mtrl-sci, cond-mat.mes-hall, physics.optics

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American Association for the Advancement of Science
Engineering and Physical Sciences Research Council (EP/M005143/1)
Engineering and Physical Sciences Research Council (EP/L015978/1)
D.D. and R.H.F. acknowledge support from the Department of Physics (Cambridge) and the King Abdulaziz City for Science and Technology–Cambridge University Joint Centre of Excellence. L.Y. thanks the Singapore Agency for Science, Technology and Research (A*STAR) for a Ph.D. studentship. J.M.R. acknowledges support from the Winton Program for the Physics of Sustainability. J.P.H.R. acknowledges the Cambridge NanoDTC (grant EP/L015978/1). M.L. acknowledges support by the Academy of Finland (project 251448). The computations were made possible by use of the Finnish Grid and Cloud Infrastructure. This work was supported by the Engineering and Physical Sciences Research Council (grant no. EP/M005143/1) and the European Research Council (ERC). M.B. is an ERC Advanced Investigator Award holder (grant no. 338944-GOCAT). D.C. and S.J. acknowledge support from the Royal Society (grant nos. UF130278 and RG140472).
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