Repository logo

Suppression of Dexter transfer by covalent encapsulation for efficient matrix-free narrowband deep blue hyperfluorescent OLEDs

Published version

Repository DOI

Change log


Congrave, Daniel G.  ORCID logo
Gillett, Alexander J.  ORCID logo
Montanaro, Stephanie  ORCID logo
Francis, Haydn E. 


Hyperfluorescence shows great promise for the next generation of commercially feasible blue organic light-emitting diodes, for which eliminating the Dexter transfer to terminal emitter triplet states is key to efficiency and stability. Current devices rely on high-gap matrices to prevent Dexter transfer, which unfortunately leads to overly complex devices from a fabrication standpoint. Here we introduce a molecular design where ultranarrowband blue emitters are covalently encapsulated by insulating alkylene straps. Organic light-emitting diodes with simple emissive layers consisting of pristine thermally activated delayed fluorescence hosts doped with encapsulated terminal emitters exhibit negligible external quantum efficiency drops compared with non-doped devices, enabling a maximum external quantum efficiency of 21.5%. To explain the high efficiency in the absence of high-gap matrices, we turn to transient absorption spectroscopy. It is directly observed that Dexter transfer from a pristine thermally activated delayed fluorescence sensitizer host can be substantially reduced by an encapsulated terminal emitter, opening the door to highly efficient ‘matrix-free’ blue hyperfluorescence.


Acknowledgements: P. L. D. Santos and D. Credgington are acknowledged for their contribution to important discussion at the beginning of this project. A. P. Monkman is acknowledged for the use of facilities at Durham University for the time-resolved PL measurements. H.-H.C. acknowledges George and Lilian Schiff Foundation for PhD studentship funding. D.G.C. acknowledges the Herchel Smith fund for an early career fellowship. A.J.G. thanks the Leverhulme Trust for an Early Career Fellowship (ECF-2022-445). V.R.-G. acknowledges the Faraday Institution Degradation Project (grant no. FIRG001 and FIRG024). J.Y. acknowledges support from a UK Research and Innovation (UKRI) Frontier Grant (no. EP/X029900/1), awarded via the European Research Council Starting Grant 2021 scheme. This work was supported by the Engineering and Physical Sciences Research Council (EPSRC, grant nos. EP/M005143/1 and EP/S003126/1). H.-H.C. and R.H.F. acknowledge the European Research Council for European Union’s Horizon 2020 research and innovation programme grant agreement no. 101020167.

Funder: George and Lilian Schiff Foundation for Ph.D. studentship funding

Funder: Herchel Smith fund


Journal Title

Nature Materials

Conference Name

Journal ISSN


Volume Title



Nature Publishing Group UK
RCUK | Engineering and Physical Sciences Research Council (EPSRC) (EP/S003126/1)
Leverhulme Trust (ECF-2022-445)