Efficient pure blue hyperfluorescence devices utilizing quadrupolar donor-acceptor-donor type of thermally activated delayed fluorescence sensitizers

The hyperfluorescence (HF) system has drawn great attention in display technology. However, the energy loss mechanism by low reverse intersystem crossing rate (kRISC) and the Dexter energy transfer (DET) channel is still challenging. Here, we demonstrate that this can be mitigated by the quadrupolar donor-acceptor-donor (D-A-D) type of thermally activated delayed fluorescence (TADF) sensitizer materials, DBA-DmICz and DBA-DTMCz. Further, the HF device with DBA-DTMCz and ν-DABNA exhibited 43.9% of high maximum external quantum efficiency (EQEmax) with the Commission Internationale de l'Éclairage coordinates of (0.12, 0.16). The efficiency values recorded for the device are among the highest reported for HF devices. Such high efficiency is assisted by hindered DET process through i) high kRISC, and ii) shielded lowest unoccupied molecular orbital with the presence of two donors in D-A-D type of skeleton. Our current study provides an effective way of designing TADF sensitizer for future HF technology.


Supplementary Tables
Supplementary Table 1    The rate constant of FRET and DET can be calculated by: 3 The decay rates of singlet (S1) and triplet (T1) excitons densities can be described by equation (1) and (2).
Where 1 and 2 are the prompt intensity and delayed intensity, respectively.
The decay rates for prompt and delayed fluorescence can be expressed as: and S5 can give:

General information and characterization
All reagents were purchased from commercial suppliers, Sigma-Aldrich, TCI (SEJINCI) and SK chemicals, and they were used without further purification otherwise stated. All solvents were used without additional purification. Silica filtration used silica with a mesh size of 200-300. All reaction progress were monitored by using thin layer chromatography (TLC). High-resolution mass spectra were performed using JEOL JMS-600W Gas Chromatography Mass spectrometer. 13 C NMRs of DBA-DmICz and DBA-DTMCz were not able to record due to their poor solubility in common NMR solvents.

Device fabrication
Prior spectroradiometer. All measurements were performed in ambient conditions.

Theoretical Calculation
All the molecular simulations were performed using the Schrödinger 2022-1 program. The optimized geometry of ground state, and HOMO, LUMO distribution were calculated using the "Optimization" tool at the B3LYP/6-31G level. The energy levels of HOMO, LUMO, S1, and T1 energies were calculated by "Optoelectronics Calculations" tool at the B3LYP/6-31G level.
NTO calculation and transition dipole moments were performed by "Single Point Energy" tool at the PBE0/6-31G level. Spin-orbit coupling matrix element value was calculated by the 2-bromo-4,6-dimethylaniline 1D (4 g, 19.99 mmol), 1-iodo-2,4-dimethylbenzene 2D (4.87 g, 20.99 mmol), tris(dibenzylideneacetone)dipalladium(0) (1.09 g, 1.19 mmol), tri-tertbutylphosphonium tetrafluoroborate (0.69 g, 2.39 mmol) and sodium tert-butoxide (3.45 g, 35.98 mmol) was added into a two neck round bottom flask equipped with a condenser, and subjected to vacuum for 10 minutes. Anhydrous toluene of 30 mL was injected followed by argon purging. The mixture was stirred at 100℃ for 4 hours and reaction progress was monitored using thin layer chromatography. Then, mixture of tris(dibenzylideneacetone) dipalladium(0) (0.545 g, 0.59 mmol) and tri-tert-butylphosphonium tetrafluoroborate (0.345 g, 1.19 mmol) in 5 mL toluene was added in to the above mixture and kept string at the same temperature for another 10 hours. After 14 hours of total reaction, the reaction mixture was filtered through a silica pad. Then, worked up using dichloromethane (60 mL) and water (25 mL) twice. The collected organic layer was dried over anhydrous sodium sulfate. After filtration, and anhydrous toluene (20 mL) were added in to a dried two neck round bottom flask equipped with a condenser at room temperature. Then, the above mixture kept stirring at 100℃ for 10 hours under an inert condition. Crude mixture was worked up using dichloromethane and water.
Collected organic layer was dried over anhydrous magnesium sulfate, and concentrated after the filtration. Finally, the crude mixture was purified using toluene and n hexane. Yield: