Revisiting the Role of Charge Transfer and Local Excitations in Thermally Activated Delayed Fluorescence

Thermally activated delayed fluorescence (TADF) is a phenomenon that relies on the upconversion of triplet excitons to singlet excitons by means of reverse intersystem crossing (rISC). It has been shown both experimentally and theoretically that the TADF mechanism depends on the interplay between charge transfer and local excitations. However, the difference between the diabatic and adiabatic character of the involved excited states is rarely discussed in the literature. Here, we develop a diabatization procedure to implement a 4-state model Hamiltonian to a set of TADF molecules. We provide physical interpretation for the Hamiltonian elements and show their dependence on the electronic state of the equilibrium geometry. We also demonstrate how vibrations affect TADF efficiency by modifying the diabatic decomposition of the molecule. Finally, we provide a simple model that connects the diabatic Hamiltonian to the electronic properties relevant to TADF and show how such relationship translates into different optimization strategies for rISC, fluorescence and overall TADF performance.

Asymmetric Sky-Blue Thermally Activated Delayed Fluorescence Emitters Bearing Tris(triazolo)triazine Moiety for Solution Processable Organic Light-Emitting Diodes

Efficient blue thermally activated delayed fluorescence (TADF) emitter is still a challenge in solution-processed organic light-emitting diodes (OLEDs). In this contribution, two asymmetric molecules of TTT-Ac and TTT-2Ac were synthesized...

Solution-processable orange-red thermally activated delayed fluorescence emitters with 3,6-disubstituted carbazole for highly efficient OLEDs with low efficiency roll-off

The progress of orange-red thermally activated delayed fluorescence (TADF) emitters for solution-processed organic light-emitting diodes (OLEDs) is still lagged behind blue and green materials in terms of device efficiency. In...

Benzonitrile-based AIE polymer host with simple synthesis process for high-efficiency solution-processable green and blue TADF organic light emitting diodes

Polymer host material have great potential for enable small molecular thermally activated delayed fluorescence (TADF) emitters to construct solution-processed organic light-emitting diodes (OLEDs). Herein, four novel benzonitrile-based polymer host, P4CzCN-PA,...

Overcome energy loss of thermally activated delayed fluorescence sensitized-OLEDs by developing fluorescence dopant with a small singlet-triplet energy splitting

TADF-sensitizing-fluorescence (TSF) strategy suffered a disturbing energy loss causing by the T1 states of fluorescence dopant (FD) due to its low T1-state energy and forbidden of radiative transition. We supposed...