Bis-Ortho-Donor-Modification of Boracyclic π-Electron Systems beyond Steric Protection to Produce Thermally Activated Delayed Fluorescence Materials.

Polycyclic π-conjugated compounds that contain tricoordinate boron atoms at their periphery represent an attractive class of materials with electron-accepting character. Their molecular design generally requires the introduction of a bulky aryl group onto the boron atom, where it provides predominantly kinetic stabilization. The addition of extra functionality to the aryl group on the boron atom can be expected to further expand the potential utility of this class of materials.

Ultrafast Triplet-Singlet Exciton Interconversion in Narrowband Blue Organoboron Emitters Doped with Heavy Chalcogens.

Narrowband emissive organoboron emitters featuring the multi-resonance (MR) effect have now become a critical material component for constructing high-performance organic light-emitting diodes (OLEDs) with pure emission colors. These MR organoboron emitters are capable of exhibiting high-efficiency narrowband thermally activated delayed fluorescence (TADF) by allowing triplet-to-singlet reverse intersystem crossing (RISC). However, RISC involving spin-flip exciton upconversion is generally the rate-limiting step in the overall TADF; hence, a deeper understanding and precise control of the RISC dynamics are ongoing crucial challenges.

Wide-Range Color Tuning of Narrowband Emission in Multi-resonance Organoboron Delayed Fluorescence Materials through Rational Imine/Amine Functionalization.

Establishing a simple and versatile design strategy to finely modulate emission colors while retaining high luminescence efficiency and color purity remains an appealing yet challenging task for the development of multi-resonance-induced thermally activated delayed fluorescence (MR-TADF) materials. Herein, we demonstrate that the strategic introduction of electron-withdrawing imine and electron-donating amine moieties into a versatile boron-embedded 1,3-bis(carbazol-9-yl)benzene skeleton enables systematic hypsochromic and bathochromic shifts of narrowband emissions, respectively. By this method, effective electroluminescence color tuning was accomplished over a wide visible range from deep-blue to yellow (461-571 nm), using the same MR molecular system, without compromising very narrow spectral features.

Fused-Nonacyclic Multi-Resonance Delayed Fluorescence Emitter Based on Ladder-Thiaborin Exhibiting Narrowband Sky-Blue Emission with Accelerated Reverse Intersystem Crossing.

Developing organic luminophores with unique capability of strong narrowband emission is both crucial and challenging for the further advancement of organic light-emitting diodes (OLEDs). Herein, a nanographitic fused-nonacyclic π-system (BSBS-N1), which was strategically embedded with multiple boron, nitrogen, and sulfur atoms, was developed as a new multi-resonance thermally activated delayed fluorescence (MR-TADF) emitter. Narrowband sky-blue emission with a peak at 478 nm, full width at half maximum of 24 nm, and photoluminescence quantum yield of 89 % was obtained with BSBS-N1.