Influence of Introduction of an Exciton Capture Layer in the Donor on the Performance of Exciplex Upconversion‐Type Organic Light‐Emitting Diodes

Further development of organic light‐emitting diodes (OLEDs) requires a reduction in driving voltage. Exciplex upconversion‐type OLEDs (ExUC‐OLEDs), which are actively utilized to form exciplexes at the donor/acceptor interface, are an optimal solution for reducing the driving voltage. However, a ph...

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Bibliographic Details
Published in:Physica status solidi. A, Applications and materials science Applications and materials science, 2023-12, Vol.220 (24), p.n/a
Main Authors: Masuda, Teppei, Morimoto, Masahiro, Naka, Shigeki
Format: Article
Language:English
Subjects:
Diffusion layers
Electric potential
Emitters
Energy gap
exciplex upconversion
Excitons
Organic light emitting diodes
triplet state
ultralow voltage
Upconversion
Voltage
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Summary:Further development of organic light‐emitting diodes (OLEDs) requires a reduction in driving voltage. Exciplex upconversion‐type OLEDs (ExUC‐OLEDs), which are actively utilized to form exciplexes at the donor/acceptor interface, are an optimal solution for reducing the driving voltage. However, a phenomenon that cannot be explained by simple exciton diffusion is observed in these devices. Herein, an exciton capture layer is inserted into the emitter (donor) layer of ExUC‐OLEDs to elucidate the exciton diffusion mechanism. All ExUC‐OLEDs emit light via triplet–triplet upconversion (TTU) and at more than half the applied voltage (1 V) of the energy gap of the emitter material. In addition, long‐range exciton diffusion of up to 40 nm is confirmed by TTU and singlet fission contributions. In exciplex upconversion‐type organic light‐emitting diodes, emission is efficient at 10 nm from the donor/acceptor (D/A) interface. The exciton‐capture (red emission) layer 40 nm away from the D/A interface emits light, indicating that excitons diffuse over 40 nm. This cannot be explained by simple exciton diffusion and is attributed to the contribution of long‐lived triplet excitons.
ISSN:1862-6300
1862-6319
DOI:10.1002/pssa.202300239