Integrating Asymmetric O-B-N Unit in Multi-Resonance Thermally Activated Delayed Fluorescence Emitters towards High-Performance Deep-Blue Organic Light-Emitting Diodes.

Developing deep-blue thermally activated delayed fluorescence (TADF) emitters with both high efficiency and color purity remains a formidable challenge. Here, we proposed a design strategy by integrating asymmetric oxygen-boron-nitrogen (O-B-N) multi-resonance (MR) unit into traditional N-B-N MR molecules to form a rigid and extended O-B-N-B-N MR π-skeleton. Three deep-blue MR-TADF emitters of OBN, NBN and ODBN featuring asymmetric O-B-N, symmetric N-B-N and extended O-B-N-B-N MR units were synthesized through the regioselective one-shot electrophilic C-H borylation at different positions of the same precursor.

Solution-Processable Chiral Boron Complexes for Circularly Polarized Red Thermally Activated Delayed Fluorescent Devices.

Circularly polarized luminescence (CPL) molecules, especially those with thermally activated delayed fluorescence (TADF) properties, have attracted considerable attention due to their great potential for chiroptical organic light emitting diode (OLED) devices. Here we developed a new pair of TADF emitters with CPL based on boron complexes using chiral donor (cD) binaphthalene, acceptor (A) biphenyl boron β-diketonate, and donor (D) biphenylamine in a cD-A-D architecture. With this design, both efficient intramolecular charge transfer (ICT) and chiral ICT for high-performance CPL were established, leading to high dissymmetry factors (||) up to 2.

Modulating Tri-Mode Emission for Single-Component White Organic Afterglow.

Achieving single-component white organic afterglow remains a great challenge owing to the difficulties in simultaneously supporting long-lived emissions from varied excited states of a molecule for complementary afterglow. Here, an extraordinary tri-mode emission from the radiative decays of singlet (S ), triplet (T ), and stabilized triplet (T ) excited states was proposed to afford white afterglow through modulating the singlet-triplet splitting energy (ΔE ) and exciton trapping depth (E ). Low-lying T * for yellow afterglow was constructed by H-aggregation engineering with large E and trace isomer doping, while high-lying T and S for blue afterglow with thermally activated emission feature were realized by reducing ΔE through donor-acceptor molecular design.

Near-Infrared-Excitable Organic Ultralong Phosphorescence through Multiphoton Absorption.

Organic ultralong room-temperature phosphorescence (OURTP) with a long-lived triplet excited state up to several seconds has triggered widespread research interests, but most OURTP materials are excited by only ultraviolet (UV) or blue light owing to their unique stabilized triplet- and solid-state emission feature. Here, we demonstrate that near-infrared- (NIR-) excitable OURTP molecules can be rationally designed by implanting intra/intermolecular charge transfer (CT) characteristics into H-aggregation to stimulate the efficient nonlinear multiphoton absorption (MPA). The resultant upconverted MPA-OURTP show ultralong lifetimes over 0.

Constructing Donor-Resonance-Donor Molecules for Acceptor-Free Bipolar Organic Semiconductors.

Organic semiconductors with bipolar transporting character are highly attractive as they offer the possibility to achieve high optoelectronic performance in simple device structures. However, the continual efforts in preparing bipolar materials are focusing on donor-acceptor (D-A) architectures by introducing both electron-donating and electron-withdrawing units into one molecule in static molecular design principles. Here, we report a dynamic approach to construct bipolar materials using only electron-donating carbazoles connected by N-P=X resonance linkages in a donor-resonance-donor (D-r-D) structure.

Thermally activated triplet exciton release for highly efficient tri-mode organic afterglow.

Developing high-efficient afterglow from metal-free organic molecules remains a formidable challenge due to the intrinsically spin-forbidden phosphorescence emission nature of organic afterglow, and only a few examples exhibit afterglow efficiency over 10%. Here, we demonstrate that the organic afterglow can be enhanced dramatically by thermally activated processes to release the excitons on the stabilized triplet state (T) to the lowest triplet state (T) and to the singlet excited state (S) for spin-allowed emission. Designed in a twisted donor-acceptor architecture with small singlet-triplet splitting energy and shallow exciton trapping depth, the thermally activated organic afterglow shows an efficiency up to 45%.

Star-Shaped Boron-Containing Asymmetric Host Materials for Solution-Processable Phosphorescent Organic Light-Emitting Diodes.

Boron-containing compounds have attracted considerable attention because of their electron-accepting properties, and they are widely used in a variety of fields. However, due to the essential requirement to protect the empty p-orbital of the boron atom using large steric hindrance or rigid groups, borane derivatives generally show poor solubility and are rarely reported as acceptor units to construct bipolar host materials for phosphorescent organic light-emitting diodes (PhOLEDs). Here, a combined star-shaped and asymmetric donor-acceptor molecular design strategy to improve the solubility and fine tune the optical and electronic properties of boron-containing materials is presented.

Selenide-containing organic resonance molecules as turn-on fluorescent probes for the selective detection of hypochlorous acid.

A new series of N-P[double bond, length as m-dash]Se resonance-based fluorescent molecules were developed and used for the detection of hypochlorous acid (HClO) with rapid response and high selectivity. These Se-containing molecules can selectively detect trace amounts of HClO in nM, showing significantly strengthened fluorescence due to the enhanced resonance variation with an increased distance between the fluorophore and Se. The design of N-P[double bond, length as m-dash]Se resonance molecules in donor-resonance-acceptor (D-r-A) architectures could be an important way to develop high-performance turn-on fluorescent probes for HClO detection.