Search Results (38)

Organic light-emitting diodes (OLEDs) have the advantages of high efficiency and high color purity, which gives them great potential and application prospects in the field of display technology, and thus they have been of wide interest for scholars and industry. Due to their nature, when using the first generation of fluorescent materials, only 25% of the excitons are used, while the rest are wasted, meaning the device efficiency does not exceed 25%. The second generation of phosphorescent materials solves this problem by utilizing 25% singlet excitons while utilizing 75% triplet excitons, achieving 100% internal quantum efficiency. Therefore, a third generation of materials, namely Thermally Activated Delayed Fluorescence (TADF) materials, has been developed, and these are able to use the small singlet–triplet energy gap to allow excitons on the triplet state to upconvert back to the single state, which improves the utilization of triplet excitons. These TADF materials can also reach 100% maximum internal quantum efficiency, but they have many problems, such as low color purity and serious efficiency roll-off. Therefore, researchers have designed hyperfluorescent materials, which possess high efficiency, high color purity, and a long lifetime, showing tremendous potential and application prospects in the field of display technology. This report takes hyperfluorescent OLEDs as the entry point and the molecular design and luminescence mechanism of hyperfluorescent materials are reviewed, considering blue, green, red, and white light. Full article

Dual-mode fluorescent materials are vital in bioimaging, sensing, displays, and lighting, owing to their efficient emission of visible or near-infrared light. Traditional optimization methods, including empirical experiments and quantum chemical computations, suffer from high costs, high labor intensities, and difficulties capturing complex relationships among molecular structures, synthesis parameters, and key photophysical properties. In this review, fundamental principles, key methodologies, and representative applications of machine learning (ML) in predicting fluorescent material performance are systematically summarized. The core ML techniques covered include supervised regression, neural networks, and physics-informed hybrid frameworks. The representative fluorescent materials analyzed encompass aggregation-induced emission (AIE) luminogens, thermally activated delayed fluorescence (TADF) emitters, quantum dots, carbon dots, perovskites, and inorganic phosphors. This review details the modeling approaches and typical workflows—such as data preprocessing, descriptor selection, and model validation—and highlights algorithmic optimization strategies such as data augmentation, physical constraints embedding, and transfer learning. Finally, prevailing challenges, including limited high-quality data availability, weak model interpretability, and insufficient model transferability, are discussed. Full article

Recent advancements in thermally activated delayed fluorescence (TADF) materials and mechanochromic materials have significantly enhanced the efficiency and versatility of light-emitting electrochemical cells (LECs) and organic light-emitting diodes (OLEDs). TADF materials have enabled efficiency improvements, achieving an internal quantum efficiency (IQE) of nearly 100% by utilizing both singlet and triplet excitons. Meanwhile, mechanochromic materials exhibit reversible optical changes upon mechanical stimuli, making them promising for stress sensing, encryption, and flexible electronics. The synergistic integration of TADF and mechanochromic materials in OLEDs and LECs has led to enhanced efficiency, stability, and multifunctionality in next-generation lighting and display technologies. This narrative review explores recent breakthroughs in devices that incorporate both TADF and mechanochromic materials as emitters. Particular attention is given to the molecular design that enable both TADF and mechanochromic properties, as well as optimal device structures and performance parameters. Moreover, this review discusses the only LEC fabricated so far using a TADF-mechanochromic emitter, highlighting its performance and potential. Finally, the report concludes with an outlook on the future commercial applications of these materials, particularly in wearable electronics and smart display technologies. Full article

We report the molecular design and synthesis of a novel selenium-containing multi-resonance thermally activated delayed fluorescence (MR-TADF) host material, 3,6-di-tert-butyl-9,16-dioxa-15-selena-4b-boraindeno[2,1-a]naphtho[3,2,1-de]anthracene (TDBA-SePh), for green and red phosphorescent organic light-emitting diodes (PhOLEDs). By incorporating selenium into the DOBNA-based MR-TADF backbone, the reverse intersystem crossing (RISC) process was effectively activated, leading to enhanced utilization of triplet excitons. The corresponding RISC rate was determined to be 3.91 × 10⁴ s⁻¹. When applied to PhOLED devices, TDBA-SePh-based green and red OLEDs exhibited higher external quantum efficiency (EQE) and reduced efficiency roll-off compared to conventional mCP-based host materials. At a luminance of 1000 cd m⁻², the green and red devices exhibited roll-off values of 2.5% and 4.3%, respectively. This improvement is attributed to the incorporation of selenium as a heteroatom, which accelerates the RISC process, thereby suppressing triplet-triplet annihilation (TTA). These results suggest that adopting a similar molecular design strategy can not only reduce efficiency roll-off but also enhance device efficiency and operational stability, offering significant potential for future OLED applications. Full article

Recent advances in electrochemiluminescence (ECL) leveraging thermally activated delayed fluorescence (TADF) have highlighted its potential for near-unity exciton harvesting. However, there are still very limited examples of TADF-ECL emitters. We present a rigid diboron-embedded multiple-resonance TADF emitter, which exhibits blue–green emission at 493 nm with a remarkably narrow bandwidth (FWHM = 22 nm) and minimized singlet-triplet energy gap (ΔE_ST = 0.2 eV), achieving a 67% photoluminescence quantum yield. DFT calculations confirm the short-range charge transfer, enabling narrowband emission. Co-reactant-dependent ECL shows that tripropylamine (TPrA) improves the ECL efficiency from 11% (annihilation) to 51%, while benzoyl peroxide (BPO) yields 1% due to poor radical stabilization. ECL spectra align with photoluminescence, confirming the singlet-state dominance without exciplex interference. TPrA enhances stable radical formation and energy transfer, whereas BPO induces non-radiative losses. These findings establish molecular rigidity and co-reactant selection as pivotal factors in developing high-performance TADF-ECL systems, providing fundamental guidelines for designing organic electrochemiluminescent materials with optimized exciton harvesting efficiency. Full article

Blue exciplexes, a critical innovative component in organic light-emitting diodes (OLEDs) technology, exhibit substantial potential for enhancing device efficiency, reducing driving voltage, and simplifying structural designs. This article reviews the pivotal role of blue exciplexes in OLEDs, analyzing their unique advantages and challenges as emitters and host materials. Through optimized molecular design, blue exciplexes achieve high color purity and emission efficiency, surpassing conventional fluorescent materials. Additionally, their wide energy bands and high triplet energy provide opportunities to improve the performance of sky-blue, deep-blue, and white OLEDs. However, limitations in deep-blue efficiency, material degradation due to high-energy excitons, and spectral red-shift pose significant challenges to their development. This review offers a comprehensive perspective and research reference on the photophysical mechanisms of blue exciplexes and their applications in display and lighting fields. Full article

Thermally activated delayed fluorescence (TADF) materials with high photoluminescence quantum yields and a fast reverse intersystem crossing (RISC) are of the highest interest for organic light-emitting diodes (OLEDs). In the past decade, triaryl boranes with multiple resonance effect (MR) have captured significant attention. The efficiency of MR-TADF emitters strongly depends on small singlet–triplet energy gaps (ΔE_ST), but also on large reverse intersystem crossing (RISC) rate constants (k_RISC). The latter effect has strongly been focused on very recently and has drawn attention to heavier elements, including sulfur and selenium, the large spin–orbit coupling (SOC) of which accelerates RISC effects. Within the context of MR-TADF emitters, the 5,9-X₂-13b-boranaphtho [3,2,1-de]anthracene scaffold (X-B-X, X = donor heteroatom, e.g., N, O, S, Se) has been recognized as a promising narrowband-emissive TADF material. However, the incorporation of sulfur and selenium as highly SOC-inducing elements has proven to be difficult. Most synthetic strategies apply protocols initially suggested by Hatakeyama to obtain nitrogen- and oxygen-doped materials. We present an alternative route over the established methodology, which affords highly sought-after sulfur- and selenium-doped materials with a high yield and purity. Full article

Organic light-emitting diodes (OLEDs) have emerged as one of the dominant technologies in displays due to their high emission efficiency and low power consumption. However, the development of blue color emitters has fallen behind that of red and green emitters, posing challenges in achieving optimal efficiency, stability, and accessibility. In this context, thermally activated delayed fluorescence (TADF) emitters hold promise as a potential solution for cost-effective, exceptionally efficient, and stable blue OLEDs due to their potential high efficiency and stability. TADF is a principle where certain organic materials can efficiently convert both singlet and triplet excitons, theoretically achieving up to 100% internal quantum efficiency. This research focused on diphenyl sulfone derivatives with carbazole groups as TADF compounds. Quantum chemical calculations and photoluminescence properties show the potential TADF properties of the molecules. New materials exhibit glass transition temperatures that would classify them as molecular glasses. Depending on the structure of the molecule, the photoluminescence emission is in the blue or green spectral region. Organic light-emitting diodes were fabricated from neat thin films of emitters by the wet casting method. The best performance in the deep blue emission region was achieved by a device with a turn-on voltage of 4 V and a maximum brightness of 178 cd/m². In the blue-green emission region, the best performance was observed by an OLED with a turn-on voltage of 3.5 V, reaching a maximum brightness of 660 cd/m². Full article

The research on boron/nitrogen (B/N)-based multiresonance thermally activated delayed fluorescence (MR-TADF) emitters has been a prominent topic due to their narrowband emission and high luminous efficiency. However, devices derived from the common types of narrowband TADF materials often experience an efficiency roll-off, which could be ascribed to their relatively slow triplet–singlet exciton interconversion. Since inserting the heavy Se atom into the B/N scheme has been a proven strategy to address the abovementioned issues, herein, extensive density functional theory (DFT) and time-dependent DFT (TD-DFT) simulations have been employed to explore the effects of the structural modification on a series of structurally modified selenium-doped derivatives. Furthermore, the two-layered ONIOM (QM/MM) model has been employed to study the pressure effects on the crystal structure and photophysical properties of the pristine CzBSe. The theoretical results found that the introduced tert-butyl units in Cz-BSeN could result in a shorter charge transfer distance and smaller reorganization energy than the parent CzBSe. In contrast to directly incorporating the o-carborane (Cb) unit to CzBSe, incorporating the bridged phenyl units is important in order to achieve narrowband emissions and high luminous efficiency. The lowest three triplet excited states of CzBSe, Cz-BSeN and PhCb-BSeN all contribute to their triplet–singlet exciton conversions, resulting in a high utilization of triplet excitons. The pressure has an evident influence on the photophysical properties of the aggregated CzBSe and is favored for obtaining narrowband emissions. Our work is promised to provide a feasible strategy for designing selenium-doped derivatives with narrowband emissions and rapid triplet–singlet exciton interconversions. Full article

Organic light-emitting diode (OLED) technology has rapidly emerged in the display and lighting sectors due to its high contrast ratio, wide viewing angle, and sleek design. Beyond these attributes, OLEDs have also demonstrated crucial applications in medicine, fashion, sports, and more, leveraging their emissive properties and flexible design. As the cornerstone of full-color displays, blue OLEDs, whose performance directly impacts color rendition and saturation, have garnered significant attention from both scientific researchers and industrial practitioners. Despite the numerous advantages of OLED technology, blue OLEDs still confront formidable challenges in terms of luminous efficiency, durability, and material stability. This review examines the evolution of blue OLED materials over recent years, specifically focusing on three generations: fluorescent, phosphorescent, and thermally activated delayed fluorescence (TADF). Through molecular design, device structure optimization, and the application of innovative technologies, remarkable advancements have been achieved in enhancing the luminous efficiency, lifetime, and color purity of blue OLEDs. However, to advance commercialization, future efforts must not only ensure high efficiency and long lifetime but also improve material stability, environmental sustainability, and reduce development costs. Emerging materials such as thermally activated exciton materials and the application of hyperfluorescent (HF) OLED technology represent vital driving forces for the continuous advancement of blue OLED technology. It is anticipated that significant milestones will continue to be achieved in the development of highly efficient blue OLEDs in the future. Full article

We designed and synthesized new indolocarbazole-triazine derivatives, 9-di-tert-butyl-5,7-bis(4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl)-5,7-dihydroindolo[2,3-b]carbazole (2TRZ-P-ICz) and 3,9-di-tert-butyl-5,7-bis(5′-(4,6-diphenyl-1,3,5-triazin-2-yl)-[1,1′:3′,1″-terphenyl]-2′-yl)-5,7-dihydroindolo[2,3-b]carbazole (2TRZ-TP-ICz), as new bipolar host materials for red phosphorescent OLEDs. In the film state, 2TRZ-P-ICz and 2TRZ-TP-ICz exhibited photoluminescence maxima at 480 nm and 488 nm, respectively. The dipole moment characteristics of the new compounds under various solvent conditions were investigated using the Lippert–Mataga equation. The results showed that the dipole moment of 2TRZ-P-ICz is 26.9D, while that of 2TRZ-TP-ICz is 21.3D. The delayed fluorescence lifetimes were 0.188 μs for 2TRZ-P-ICz and 2.080 μs for 2TRZ-TP-ICz, with 2TRZ-TP-ICz showing TADF characteristics. Additionally, 2TRZ-TP-ICz was found to have a ΔEST of less than 0.2 eV. The triplet energy levels of the newly synthesized bipolar host materials were found to be 2.72 and 2.75 eV, confirming their suitability for use in red phosphorescent OLEDs. To investigate the carrier mobility of the synthesized materials, hole-only devices and electron-only devices were fabricated and tested. The hole mobility value at 1V was found to be 3.43 × 10⁻³ cm²/Vs for 2TRZ-P-ICz and 2.16 × 10⁻³ cm²/Vs for 2TRZ-TP-ICz. For electron mobility at 1V, 2TRZ-P-ICz showed a value of 4.41 × 10⁻⁹ cm²/Vs, while 2TRZ-TP-ICz exhibited a value of 9.13 × 10⁻⁹ cm²/Vs. As a result, when the new material was used as a host in red phosphorescent OLEDs, 2TRZ-TP-ICz achieved a current efficiency of 9.92 cd/A, an external quantum efficiency of 13.7%, CIE coordinates of (0.679, 0.319), and an electroluminescence maximum wavelength of 626 nm. Full article

The study developed a large emission area of flexible blue organic light-emitting diodes (BOLED) on a polyethylene terephthalate/ Indium tin oxide (PET/ITO) substrate using a polycyclic skeleton ν-DABNA Thermally Activated Delayed Fluorescence (TADF) material. Initially, a 1 × 1 cm² blue OLED was fabricated to optimize the layer thickness. The blue OLED structure consisted of PET/ITO/HATCN/TAPC/UBH-21:ν-DABNA/TPBi/LiF/Al. However, as the emission area increased to 3.5 × 3.5 cm², the current density decreased due to the resistance of PET/ITO, leading to luminance non-uniformity. To address this issue, auxiliary Au lines were added to the ITO anode to enhance current injection. Despite this, when the Au lines reached a thickness of 30 nm, average light emission was disrupted. To improve the luminescence characteristics of large-area PET/ITO OLEDs, a capping and planarization layer of PEDOT:PSS was applied. Grid uniformity revealed a significant increase in overall luminance uniformity from 74.1% to 87.4% with the addition of auxiliary Au lines. Further increases in grid line density slightly reduced uniformity but enhanced brightness, resulting in brighter, flexible, large-area blue OLED lighting panels. Full article

The ever-growing prominence and widespread acceptance of organic light-emitting diodes (OLEDs), particularly those employing thermally activated delayed fluorescence (TADF), have firmly established them as formidable contenders in the field of lighting technology. TADF enables achieving a 100% utilization rate and efficient luminescence through reverse intersystem crossing (RISC). However, the effectiveness of TADF-OLEDs is influenced by their high current density and limited device lifetime, which result in a significant reduction in efficiency. This comprehensive review introduces the TADF mechanism and provides a detailed overview of recent advancements in the development of host-free white OLEDs (WOLEDs) utilizing TADF. This review specifically scrutinizes advancements from three distinct perspectives: TADF fluorescence, TADF phosphorescence and all-TADF materials in host-free WOLEDs. By presenting the latest research findings, this review contributes to the understanding of the current state of host-free WOLEDs, employing TADF and underscoring promising avenues for future investigations. It aims to serve as a valuable resource for newcomers seeking an entry point into the field as well as for established members of the WOLEDs community, offering them insightful perspectives on imminent advancements. Full article

Over the past few decades, organic light-emitting diodes (OLEDs) find applications in smartphones, televisions, and the automotive sector. However, this technology is still not perfect, and its application for lighting purposes has been slow. For further development of the OLEDs, we designed twisted donor-acceptor-type electroactive bipolar derivatives using benzophenone and bicarbazole as building blocks. Derivatives were synthesized through the reaction of 4-fluorobenzophenone with various mono-alkylated 3,3′-bicarbazoles. We have provided a comprehensive structural characterization of these compounds. The new materials are amorphous and exhibit suitable glass transition temperatures ranging from 57 to 102 °C. They also demonstrate high thermal stability, with decomposition temperatures reaching 400 °C. The developed compounds exhibit elevated photoluminescence quantum yields (PLQY) of up to 75.5% and favourable HOMO-LUMO levels, along with suitable triplet-singlet state energy values. Due to their good solubility and suitable film-forming properties, all the compounds were evaluated as blue TADF emitters dispersed in commercial 4,4′-bis(N-carbazolyl)-1,10-biphenyl (CBP) host material and used for the formation of emissive layer of organic light-emitting diodes (OLEDs) in concentration-dependent experiments. Out of these experiments, the OLED with 15 wt% of the emitting derivative 4-(9′-{2-ethylhexyl}-[3,3′]-bicarbazol-9-yl)benzophenone exhibited superior performance. It attained a maximum brightness of 3581 cd/m², a current efficacy of 5.7 cd/A, a power efficacy of 4.1 lm/W, and an external quantum efficacy of 2.7%. Full article

Up to now, highly efficient narrowband thermally activated delayed fluorescence (TADF) molecules constructed by oxygen-bridged boron with an enhancing multiple resonance (MR) effect have been in urgent demand for solid-state lighting and full-color displays. In this work, a novel MR-TADF molecule, BNBO, constructed by the oxygen-bridged boron unit and boron–nitrogen core skeleton as an electron-donating moiety, is successfully designed and synthesized via a facile one-step synthesis. Based on BNBO as an efficient green emitter, the organic light-emitting diode (OLED) shows a sharp emission peak of 508 nm with a full-width at half-maximum (FWHM) of 36 nm and realizes quite high peak efficiency values, including an external quantum efficiency (EQE_max) of 24.3% and a power efficiency (PE_max) of 62.3 lm/W. BNBO possesses the intramolecular charge transfer (ICT) property of donor-acceptor (D-A) materials and multiple resonance characteristics, which provide a simple strategy for narrowband oxygen–boron materials. Full article