Year: 2026
Type: preprint
Abstract: Curved nitrogen-doped polycyclic aromatic hydrocarbons offer a rigid and nonplanar framework for investigating how donor identity regulates the balance between locally excited and chargetransfer states in thermally activated delayed fluorescence (TADF) emitters. Here, a pyrido[2,3b]quinoxaline unit was integrated into a dibenzo[b,f]azepine-based polycyclic aromatic hydrocarbon scaffold and functionalized with one of 3,6-di-tert-butylcarbazole (TBCzPyN-PAH), diphenylamine (DPAPyN-PAH), 9,9-dimethyl-9,10-dihydroacridine (DMAcPyN-PAH), or phenoxazine (PXZPyN-PAH) donor moieties. The resulting series provides a common acceptor framework in which the electronic and conformational properties of the peripheral donor affect the 2 energies of the excited states. Donor substitution tunes the emission maximum in toluene from 528 to 697 nm. In 2 wt% doped films in CBP, these compounds emit from 519 to 622 nm with PLQY of up to 58%. Temperature-dependent time-resolved photoluminescence confirms TADF for all investigated compounds except for the DPA derivative. Across the TADF-active series, the singlet–triplet energy gap, ΔEST, decreases from 0.22 to 0.03 eV and the delayed fluorescence lifetime shortens from 8.5 ms to 29 μs. Vacuum-deposited OLEDs with TBCzPyN-PAH showed EQEmax, of 21.6% at an electroluminescence maximum of 538 nm, whereas the device with PXZPyN-PAH emitted at 606 nm and showed a lower EQEmax of 7.2% but with a milder efficiency roll-off.
Source: ChemRxiv
Language: English
Subfield: Electrical and Electronic Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7213365058