Spatial donor/acceptor architecture for intramolecular charge-transfer emitter

Charge transfer via electron hopping from an electron donor(D)to an acceptor(A)in nanoscale,plays a crucial role in optoelectronic materials,such as organic light-emitting diodes(OLEDs)and organic photovoltaic cells(OPVs).Here,we propose a strategy for binding D/A units in space,where intramolecular charge-transfer can take place.The resulted material DM-Me-B is able to give bright emission in this molecular architecture because of the good control of D/A interaction and conformational rigidity.Moreover,DM-Me-B presents small singlet-triplet splitting energy,enabling thermally activated delayed fluorescence.Therefore,the DM-Me-B exhibits~20%maximum external quantum efficiency and low efficiency roll-off at 1000 cd/m^(2),certifying an effective strategy in controlling D/A blocks through space.

π-Stacked Thermally Activated Delayed Fluorescence Emitters with Alkyl Chain Modulation

Molecules bearing separateπ-electron donor(D)and acceptor(A)groups that undergo face-to-face D/A interactions have been utilized to develop thermally activated delayed fluorescence(TADF)materials.Theseπ-stacked D/A architectures are constructed on various scaffolds,which have either a long D/A distance or permitted conrotatory motion.Here,we develop a novel spiro-based scaffold with a short D/A distance and restricted circumvolution motions because of both the rigid spiro-scaffold and large rotation hindrance between the nearly coplanar D and A.We append different alkyl chains,which can modulate charge transfer and luminescence properties,at the nitrogen of the D moiety to develop four TADF molecules,which can modulate chargetransfer and luminescence properties.Because of the introduction of the solubilized alkyl chain,these molecules were used to fabricate solutionprocessed devices,among which a maximum external quantum efficiency of 18.9%was realized.By modulating interactions between the D/A building blocks,these TADF constructs exemplify that the alkyl side chains of TADF molecules,which used to be considered as solubilizing units,have vital impact on the optoelectronic properties and thus offer a new route to the design of solution-processable TADF emitters.