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HL: Fachverband Halbleiterphysik

HL 15: Organic Semiconductors: Optics and Photonics

HL 15.4: Vortrag

Dienstag, 10. März 2026, 10:15–10:30, POT/0006

Aggregation enhanced singlet emission in a purely organic emitter with thermally activated delayed fluorescence — •Jiacheng Gong, Xin Zhou, Kaiwen Guo, Toulik Maitra, Denis Andrienko, Gert-Jan Wetzelaer, Paul W. M. Blom, and Yungui Li — Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany

Purely organic thermally activated delayed fluorescence (TADF) emitters have gained great attentions in the field of organic light-emitting devices. However, the long-lived triplet exciton contributes to efficiency roll-off and device degradation at high current densities. Great efforts have been made to accelerate reverse intersystem crossing (rISC), while there are less studies on the increase of singlet radiative transition rate (krS). Herein, based on the benchmark TADF emitter CzDBA, it is found that it exhibits a larger krS in neat film, which is ~ 4 times faster than that in toluene with similar dielectric environment. The modelling of excited-state dynamics for electrically excited TADF emitters demonstrates that the increased krS reduces triplet and singlet densities simultaneously, while retaining high charge-to-photon conversion efficiency. Furthermore, time-resolved photoluminescence and steady-state absorption spectroscopic analysis shows that the broadened absorption feature increases the oscillator strength and hence increases krS in terms of Strickler-Berg relation. Gaussian disorder model is further applied to PL excitation spectra, and a larger disorder factor from the film samples implies that the large disorder of energetic landscape may contribute to the enhanced krS.

Keywords: organic light-emitting diodes; thermally activated delayed fluorescence; singlet radiative transition; aggregation; energy disorder