Rational Design of π-Conjugated Tricoordinated Organoboron Derivatives With Thermally Activated Delayed Fluorescent Properties for Application in Organic Light-Emitting Diodes

Abstract

A series of donor-acceptor (D-A) tricoordinated organoboron derivatives (1-10) have been systematically investigated for thermally activated delayed fluorescent (TADF)-based organic light-emitting diode (OLED) materials. The calculated results show that the designed molecules exhibit small singlet-triplet energy gap (E ST) values. Density functional theory (DFT) analysis indicated that the designed molecules display an efficient separation between donor and acceptor fragments because of a small overlap between donor and acceptor fragments on HOMOs and LUMOs. Furthermore, the delayed fluorescence emission color can be tuned effectively by introduction of different polycyclic aromatic fragments in parent molecule 1. The calculated results show that molecules 2, 3, and 4 possess more significant Stokes shifts and red emission with small E ST values. Nevertheless, other molecules exhibit green (1, 7, and 8), light green (6 and 10), and blue (5 and 9) emissions. Meanwhile, they are potential ambipolar charge transport materials except that 4 and 10 can serve as electron and hole transport materials only, respectively. Therefore, we proposed a rational way for the design of efficient TADF materials as well as charge transport materials for OLEDs simultaneously.

Photophysical Properties of Boron‐Based Chromophores as Effective Moieties in TADF Devices: A Computational Study**

“…The final spectrum is obtained by the convolution of all the vertical transitions and the corresponding oscillator strengths. Absorption spectra were modeled using B3LYP, BLYP, [38] PBE0, [54,55] M06-2X and ωB97XD functionals and 6-31 + G(d,p) basis set. To reproduce the band shape the vertical transitions from each snapshot were convoluted using Gaussian functions of fullwidth at half-length (FWHL) of 0.15 eV.…”

Boron-Based Chromophores As Effective Moieties In Optoelectronic Devices

“…The final spectrum is obtained by the convolution of all the vertical transitions and the corresponding oscillator strengths. Absorption spectra were modeled using B3LYP, BLYP, 34,36,50 PBE0, 51,52 M06-2X and ωB97XD functionals and 6-31+G(d,p) basis set. To reproduce the band shape the vertical transitions from each snapshot were convoluted using Gaussian functions of full-width at half length (FWHL) of 0.15 eV.…”

Versatile boron‐based thermally activated delayed fluorescence materials for organic light‐emitting diodes

“…In another study, two organoboron compounds 70 and 71 substituting weak electron-donating groups of the dimethylacridine units with carbazole units were reported with tunable emission colors and highly efficient blue TADF devices. [70] Compared to the widely used acridan derivatives, 10,10-diphenyl-phenazasiline is a weaker and more stable donor unit, thus resulting in blueshifted emissions. For example, Yasuda and coworkers reported a deep-blue TADF emitter 72, in which the polycyclic organoboron was employed as a weak electron acceptor and phenazasiline was used as a weak electron donor.…”