The development of intramolecular-lock strategy is an appealing task for designing efficient thermally activated delayed fluorescence (TADF) molecules, but only limited examples of intramolecular-lock strategies have been developed to aim at designing efficient TADF molecules with rigid structures, for example, introducing pyridine moieties to form intramolecular hydrogen bonding interactions, endowing molecules with large steric hinderance, introducing sp3-carbon lock.
To address this issue, Jingsong You/Zhengyang Bin et al. in the College of Chemistry, Sichuan University, put forward a "medium ring"-lock strategy to develop TADF emitters for improving the efficiency of organic light-emitting diodes (OLEDs). The installation of an electron-deficient heptagonal diimide lock onto a highly rotatable biphenyl-based emitter not only enhances electron-withdrawing ability of acceptor that decreases singlet-triplet energy gap (ΔEST), but also endows the skeleton with modest rigidity and flexibility that increases photoluminescence quantum yield (PLQY) in neat film. In particular, the integration of the diimide lock also leads to an increase in horizontal orientation factor (Θ//) from 69% to 83%
Consequently, this modified intramolecular-lock strategy enables an efficient TADF emitter to assemble high-performance non-doped OLEDs with a high external quantum efficiency of 26.2% and a power efficiency of 76.6 lm W-1.
This work is published on Angewandte Chemie International Edition, titled as “Modified Intramolecular-Lock Strategy Enables Efficient Thermally Activated Delayed Fluorescence Emitters for Non-Doped OLEDs”. Sichuan University is top institute in the address list. Prof. Jingsong You and associated Prof. Zhengyang Bin are corresponding authors, and Miss. Zhenmei Huang is the first author. This work is financially supported by financial support from the National NSF of China and the Sichuan Science and Technology Program as well as the Institutional Research Fund from Sichuan University. Thanks for Prof. Dongge Ma and Prof. Dezhi Yang from South China University of Technology for the assistance with horizontal dipole ratio measurements.
Links to: https://doi.org/10.1002/anie.202213157
