Donor–Acceptor Integration Modulates Reverse Intersystem Crossing in Multi-Resonant TADF Emitters
Year: 2026
Type: preprint
Abstract: Multi-resonant thermally activated delayed fluorescent (MR-TADF) compounds are attractive as emitters in organic light-emitting diodes (OLEDs) owing to their high photoluminescence quantum yields and narrowband emission. However, these emitters generally have moderate reverse intersystem crossing rate constants (kRISC), which causes triplet exciton accumulation and leads to, amongst other excitonic processes, triplet-triplet annihilation. This process results in significant efficiency roll-off in OLEDs at high luminance. Here, we report the photophysical properties of a 2 boron–nitrogen doped MR-TADF emitter, tCzBN, and two of its derivatives, SpAc-tCzBN and TRZ-SpAc-DBN, using time-resolved absorption and emission spectroscopy. Kinetic modelling of their photophysical behavior reveals that combining a donor–acceptor core with the MR-TADF moiety in TRZ-SpAc-DBN results in a higher kRISC than tCzBN and its donor-appended analog, SpAc-tCzBN, while preserving the narrowband emission of the MR-TADF unit. We attribute this enhancement to the lower effective adiabatic singlet–triplet energy gap (∆EST) and stronger spinorbit coupling in this molecular design.
Source: ChemRxiv
Institutions: The University of Sydney, University of St Andrews
Language: English
Subfield: Electrical and Electronic Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7215075339