11 Mar 12:16
by Pei Zhao,
Wei‐Chen Guo,
Hai‐Yan Lu,
Chuan‐Feng Chen
Conformational isomerization of the Se-based donors in a pair of enantiomers has led to multi-emission of blue, yellow and red phosphorescence. The enantiomers thus showed single-molecule white circularly polarized photoluminescence (WCPL) and also exhibited white circularly polarized electroluminescence in white organic light-emitting diodes with a color rendering index (CRI) of 82 at CIE coordinates of (0.29, 0.33).
Abstract
A pair of multi-emission enantiomers, (R)-DO-PSeZ and (S)-DO-PSeZ, was designed and synthesized by integrating Se-induced conformationally isomeric donors with a chiral carbonyl-containing acceptor into a unified molecular framework. The enantiomers showed white emission with blue, yellow and red multi-emission bands in solution and film at CIE coordinates of (0.39, 0.35) and (0.33, 0.34), respectively. Doped film of the enantiomers achieved a high photoluminescence quantum yield of 42 %, accompanied by mirror-image white circularly polarized photoluminescence (WCPPL) signals with a |gPL
| value of 2.6×10−3. Moreover, the enantiomers also showed white circularly polarized electroluminescence (WCPEL) in organic light-emitting diodes with CIE coordinates of (0.29, 0.33) and EQEmax of 3.1 %. Notably, this work represents the first single-molecule multi-emission WCPL materials and achieved the highest performance for white OLEDs based on single-molecule organic materials with phosphorescent properties. Furthermore, leveraging Bragg reflection from dual-layer cholesteric liquid crystals, the enantiomers achieved |g
PL| and |g
EL| values of 1.85 and 1.88, respectively, marking the highest reported values for WCPPL and WCPEL to date.
11 Mar 12:15
by Yue-Jian yang,
denis Ari,
Zhe-Hong yu,
Kelvine Lettelier,
Olivier Jeannin,
Qi Zheng,
Aziz Khan,
cassandre Quinton,
Dong-Ying Zhou,
Jiang Zuo-quan,
Cyril Poriel
The first application of pure hydrocarbon materials as hosts in phosphorescence-sensitized multi-resonance thermally activated delayed fluorescence (MR-TADF) OLEDs is reported. Blue MR-TADF OLEDs using either DtBuCzB or v-DABNA as emitter and either FIrpic, fac-Ir(tpz)3 or CN−Ir as sensitizer, achieved very high maximum external quantum efficiencies ranging from 29.1 % to 33.9 %, due to an excellent molecular orientation induced by the PHC hosts.
Abstract
Pure hydrocarbon (PHC) materials are a class of highly efficient and stable host materials for organic light-emitting diodes (OLEDs), composed solely of carbon and hydrogen atoms. Despite recent great advancements in PHC research, their applications are still mainly limited to phosphorescent OLEDs (PHOLEDs). High-performance blue OLEDs still pose a considerable challenge. Thus, expanding PHC materials into other types of OLEDs is critical for advancing organic electronic technologies. In this study, we designed a series of original high-triplet PHC materials based on a multi-substitution approach of the 9,9′-spirobifluorene (SBF) backbone and used them, for the first time, as a host in phosphorescence-sensitized multi-resonance thermally activated delayed fluorescence (MR-TADF) OLEDs. Devices based on the 2,6-bis(3,6-di-tert-butyl-9H-carbazol-9-yl)boron (DtBuCzB) emitter, using FIrpic or fac-Ir(tpz)3 as the sensitizer, achieved high maximum external quantum efficiency (EQEmax) values ranging from 29.1 % to 33.9 %. Additionally, blue MR-TADF OLED devices based on v-DABNA with a phosphorescent sensitizer (CN−Ir), demonstrated outstanding electroluminescent performance, with an EQEmax of approximately 31 % due to an excellent molecular orientation induced by the PHC hosts. All devices exhibited narrow full-width at half-maximum spectra and minimal efficiency roll-off. This study marks the first application of PHC materials as hosts in phosphorescence-sensitized MR-TADF OLEDs, highlighting their potential as promising candidates for next-generation blue OLEDs and offering a viable pathway to achieve high-performance devices.
11 Mar 12:15
by Jiaxin Jiang,
Yunfang Zhao,
Zhijia Li,
Yangxingyu Ye,
Zhiyuan Wu,
Feilong Jiang,
Lian Chen,
Maochun Hong
A copper(I) halide complex with thermally activated delayed fluorescence (TADF) and aggregation-induced emission (AIE) effects exhibits excellent X-ray scintillation and imaging performance, which is resulted from the joint effect of effective X-ray absorption of the heavy Cu2I2 core, high exciton utilization efficiency facilitated by the fast reverse intersystem crossing (RISC), and the effective suppression of non-radiative transitions in solid state.
Abstract
Developing solution-processable and stable scintillators with high light yields, low detection limits and high imaging resolutions holds great significance for flexible X-ray imaging. However, attaining an optimal equilibrium among X-ray absorption capacity, exciton utilization efficiency, and decay lifetime of scintillators remains a substantial challenge. Here, a new Cu(I) halide complex was synthesized in a mild condition. It exhibits intense blue thermally activated delayed fluorescence (TADF), remarkable aggregation-induced emission (AIE) characteristic, as well as good water-oxygen stability and photochemical stability. Notably, the complex shows excellent radiation resistance and efficient radioluminescence (RL) with an ultra-low detection limit of 42.5 nGyairs−1. This superior scintillation performance can be attributed to the synergistic effect of effective X-ray absorption by the heavy Cu2I2 core, the high radiation-induced exciton utilization rate in TADF process, and the remarkable suppression of non-radiative transitions by the restriction of intramolecular motions in solid state. Furthermore, the favourable solution processability of the complex facilitates the successful fabrication of a flexible film, achieving high-quality X-ray imaging with a resolution of 17.3 lp mm−1. This work highlights the potential of hybrid Cu(I) halides with AIE-TADF effects for high-energy radiation detection and imaging, opening up new avenues for the exploration of cost-effective and high-performance scintillators.
06 Mar 09:14
by Wentao Xie, Xiaosong Cao, Manli Huang, Ke Xu, Chenghao Gui, Zhanxiang Chen, Xiu-Fang Song, Yaxiong Wei, He Liu, Tao Hua, Ming Yang, Xiaojun Yin, Jingsheng Miao, and Chuluo Yang
Journal of the American Chemical Society
DOI: 10.1021/jacs.4c13264
06 Mar 09:07
by Nils Bäumer, Saeko Yamada, Soichiro Ogi, and Shigehiro Yamaguchi
Journal of the American Chemical Society
DOI: 10.1021/jacs.4c15766
06 Mar 09:05
by Zongliang Xie, Huangjun Deng, Xiangyu Ge, Zhenguo Chi, and Bin Liu
Journal of the American Chemical Society
DOI: 10.1021/jacs.5c00894
20 Feb 15:49
by Yang Yu,
Chang Wang,
Faan-Fung Hung,
Long Jiang,
Chi-Ming Che,
Junzhi Liu
Three π-extended heli(aminoborane)s (E[10]HAB-A/B/C) were synthesized to find a balance between fluorescence quantum yield (Φ
lum) and absorption/luminescence dissymmetry factors (g
abs/g
lum). These molecules exhibited remarkable photophysical properties, including high Φ
lum and narrowband emission (full width at half maximum, FWHM=16 nm), in which E[10]HAB-A boosted circularly polarized luminescence brightness (B
CPL) up to 583 M−1cm−1.
Abstract
Helical molecular carbons (HMCs) possess high absorption/luminescence dissymmetry factors (g
abs/g
lum) and significant luminescence quantum yield (Φ
lum), resulting in a high circularly polarized luminescence (CPL) brightness (B
CPL), which is essential for the development of CPL materials for practical applications. Herein, we designed and synthesized a series of boron-nitrogen (BN)-doped HMCs, named π-extended heli(aminoborane)s (E[10]HAB-A, E[10]HAB-B and E[10]HAB-C), consisting of laterally π-extended [10]helicene skeleton with alternating N and B atoms at the inner rim. The aromaticity, electronic structures, and photophysical properties of E[10]HAB-A/B/C were systematically investigated through experiments and theoretical calculations. E[10]HAB-A/B/C displayed remarkable photophysical properties, including high molar extinction coefficient and bright narrowband emission. The isolated enantiomers of E[10]HAB-A/B/C exhibited intense circular dichroism (CD) and CPL, in which E[10]HAB-A shows g
abs and g
lum values up to 0.024 and 0.017, simultaneously with high Φ
lum of 82 % and a narrow full width at half maximum of 16 nm. Accordingly, E[10]HAB-A exhibits a B
CPL as high as 583 M−1 cm−1, which is the largest value among the reported BN-doped HMCs. Our study indicates that inner rim BN-doping and π-extension are effective strategies to achieve high Φ
lum and balanced g
lum values in HMCs.
20 Feb 15:48
by Zuo-Quan Jiang,
Rui-Hong Liu,
Zi-Qi Feng,
Shi-Jie Ge,
Yu Wang,
Zhe-Hong Yu,
Jian-Rong Wu,
Hong-Yan Yan,
Dong-Ying Zhou,
Liang-Sheng Liao
Through-space conjugated (TSC) materials with highly efficient device performance and narrowband emission are still challenging. Introducing two bulky TSC blocks restrains the vibrational transitions of the multi-resonance nitrogen/carbonyl core, with full widths at half-maximum (FWHM) of 19 and 25 nm in solution. A record-high electroluminescent efficiency for a nitrogen/carbonyl system of 26.7 % with a FWHM of 23 nm was obtained within the blue spectrum.
Abstract
Organic luminescent materials featuring noncovalent through-space conjugation (TSC) have attracted considerable attention. However, the presence of multiple vibrational energy levels and weak spatial electron delocalization typically results in broad emission peaks for TSC-based emitters, significantly impeding their extensive application in optoelectronic technologies. Herein, two TSC emitters, TSFQ-TRZ and TSFQ-Ph, were synthesized by integrating a fused nitrogen/carbonyl skeleton with various adjacent arene 2,4,6-triphenyl-1,3,5-triazine (TPTRZ) and phenyl group segments through a rigid spiro spacer. These emitters exhibited narrow emissions, with full widths at half-maximum of 19 nm and 25 nm, respectively. Experimental and theoretical investigations unveiled that the TPTRZ segment introduces steric hindrance, while simultaneously suppressing molecular vibrations through intramolecular interactions—a key factor in achieving narrow emissions. Leveraging this narrow blue emission, electroluminescent devices employing TSFQ-TRZ as the emitter achieved an impressive maximum external quantum efficiency of 26.7 %, which further increased to 28.3 % when sensitized by phosphorescent emitter. This work demonstrates highly efficient, narrowband emissions from TSC-based emitters, thereby expanding their potential applications in the electroluminescence field.
17 Feb 10:00
by Sandipan Ghorai,
Soumyadip Show,
Anindita Das
Unprecedented control of circularly polarized luminescence (CPL) in two axially chiral π-conjugated fluorescent enantiomers is achieved through supramolecular self-assembly. The naphthalene monoimide (NMI) fluorophores (R-NMI and S-NMI), each equipped with two pyridyl functionalities, show solvent-dependent aggregation-induced emission enhancement (AIEE) and enhanced chiroptical properties through π-π stacking. Co-assemblies with chiral diacids (D- and L-tartaric acids) produce hydrogen-bonded helical structures, resulting in inversion and amplification of CD and CPL properties.
Abstract
Herein, we report the self-assembly and chiroptical properties of two axially chiral π-conjugated luminogens,
R-
NMI and
S-
NMI, each equipped with two pyridyl moieties for hydrogen (H)-bonding with chiral diacids. The two enantiomers display aggregation-induced emission enhancement (AIEE) and increased CD and CPL signals in the self-assembled state with a high g
lum
value of 1.5 (±0.06)×10−2 in 1:9 dioxane:methylcyclohexane. Crystallographic analysis confirmed mirror-image helical structures for
R
-NMI and
S
-NMI involving both intra- and intermolecular π-π stacking, leading to elongated hexagonal platelets. Supramolecular co-assembly of
R-
NMI with D- and L-tartaric acids (
D
-TA and
L
-TA) could remarkably modulate and invert the chiroptical properties of
R-
NMI, which is unachievable with control chiral monoacids. The co-assembled structures were driven by pyridine-carboxylic acid H-bonding as revealed from the crystal structure analysis, which was also supported by computational studies. Strikingly,
R
-NMI+D-TA leads to an exceptionally high fourfold amplification in the g
lum
value [5.4 (±0.04)×10−2] with an inverted sign, which additionally demonstrates intriguing temperature-dependent switching. In contrast,
R
-NMI+L-TA results in a threefold reduction in the g
lum
value [0.54 (±0.015)×10−3], also with an inverted sign compared to
R
-NMI alone, establishing a clear strategy for chiral discrimination between the two enantiomers of TA.
13 Feb 16:14
by Jingwen Yao,
Yuling Huang,
Haifeng Sun,
Zhiyu Wang,
Jie Xue,
Zhifeng Huang,
Shou‐Cheng Dong,
Xihan Chen,
Haipeng Lu
A series of chiral quasi-2D perovskites are reported with efficient circularly polarized luminescence (CPL) in films and circularly polarized electroluminescence (CPEL) in spin-LEDs in the red to near-infrared spectrum region. Spectroscopic studies show that the CPL and CPEL originate from an energy and spin funnel process in the chiral quasi-2D perovskites.
Abstract
Spin light-emitting diodes (spin-LEDs) are important for spin-based electronic circuits as they convert the carrier spin information to optical polarization. Recently, chiral-induced spin selectivity (CISS) has emerged as a new paradigm to enable spin-LED as it does not require any magnetic components and operates at room temperature. However, CISS-enabled spin-LED with tunable wavelengths ranging from red to near-infrared (NIR) has yet to be demonstrated. Here, chiral quasi-2D perovskites are developed to fabricate efficient spin-LEDs with tunable wavelengths from red to NIR region by tuning the halide composition. The optimized chiral perovskite films exhibit efficient circularly polarized luminescence from 675 to 788 nm, with a photoluminescence quantum yield (PLQY) exceeding 86% and a dissymmetry factor (g
lum) ranging from 8.5 × 10−3 to 2.6 × 10−2. More importantly, direct circularly polarized electroluminescence (CPEL) is achieved at room temperature in spin-LEDs. This work demonstrated efficient red and NIR spin-LEDs with the highest external quantum efficiency (EQE) reaching 12.4% and the electroluminescence (EL) dissymmetry factors (g
EL) ranging from 3.7 × 10−3 to 1.48 × 10−2 at room temperature. The composition-dependent CPEL performance is further attributed to the prolonged spin lifetime as revealed by ultrafast transient absorption spectroscopy.
13 Feb 16:04
by Zhengqi Xiao,
Yang Zou,
Zhanxiang Chen,
Jingsheng Miao,
Yuntao Qiu,
Zhongyan Huang,
Xiaosong Cao,
Xiaojun Peng,
Chuluo Yang
TADF sensitizers targeting deep-blue emitters are designed by combining the advantages of short-range and long-range charge-transfer excited states. The resulting sensitizers enable high-performance deep-blue OLEDs with BT. 2020 blue gamut together with external quantum efficiency approaching 40%.
Abstract
The hyperfluorescence (HF) technology holds great promise for the development of high-quality organic light-emitting diodes (OLEDs) for their excellent color purity, high efficiency, and low-efficiency roll-off. Sensitizer plays a crucial role in the performance of HF devices. However, designing sensitizers with simultaneous high photoluminescence quantum yield (PLQY), rapid radiative decay (k
r), and fast reverse intersystem crossing rate (k
RISC) poses a great challenge, particularly for the thermally activated delayed fluorescence (TADF) sensitizers targeting deep-blue HF device. Herein, by introducing a boron-containing multi-resonance-type acceptor into the multi-tert-butyl-carbazole encapsulated benzene molecular skeleton, two TADF emitters featuring hybridized multi-channel charge-transfer pathways, including short-range multi-resonance, weakened through-bond, and compact face-to-face through-space charge-transfer. Benefiting from the rational molecular design, the proof-of-concept sensitizers exhibit simultaneous rapid k
r of 5.3 × 107 s−1, fast k
RISC up to 5.9 × 105 s−1, a PQLY of near-unity, as well as ideal deep-blue emission in both solution and film. Consequently, the corresponding deep-blue HF devices not only achieve chromaticity coordinates that fully comply with the latest BT. 2020 standards, but also showcase record-high maximum external quantum efficiencies nearing 40%, along with suppressed efficiency roll-off.
13 Feb 15:46
by Hui Wang,
Sen Lin,
Jia‐Xiong Chen,
Xiao‐Yao Hao,
Xiao‐Chun Fan,
Yi‐Zhong Shi,
Jia Yu,
Xian‐Kai Chen,
Kai Wang,
Xiao‐Hong Zhang
The first example of a quasiplanar donor–acceptor-type red/near-infrared (NIR) thermally activated delayed fluorescence emitter is presented in a stepwise planarity manner via a spiro-locked C─C covalent bond linking strategy combined with the subtle management of intermolecular noncovalent bonds. The corresponding doped and nondoped organic light-emitting diodes exhibited state-of-the-art red/NIR performance, with record-high external quantum efficiencies of 38.7% and 12.6% and emission peaks at 631 and 730 nm, respectively.
Abstract
Quasiplanar donor–acceptor (D–A) thermally activated delayed fluorescence (TADF) molecules are appealing candidates for efficient red/near-infrared (NIR) emitters but have not been realized. Herein, for the first time, a stepwise approach to achieve this goal via a spiro-locked C─C covalent bond linking strategy combined with the subtle management of intermolecular C─H···CN noncovalent bonds in condensed states is presented. This synergetic effect enables the newly developed molecule, DCN-SAC, to not only attain nearly unity photoluminescence quantum yield, with a horizontal dipole ratio of up to 89% at 5 wt% doped conditions but also achieve a quasiplanar configuration with high-exciton-harvesting J-aggregates under neat condensed conditions. The optimized organic light-emitting diode (OLED) using DCN-SAC as the dopant furnishes a topmost external quantum efficiency (EQE) of 38.7% at 631 nm among all red OLEDs based on TADF materials. More importantly, a DCN-SAC-based nondoped OLED affords a remarkable EQE of 12.6% with an emission peak at 730 nm, which sets a record-breaking value among all previously reported nondoped TADF devices in the similar emission region. These findings reveal the effectiveness and great potential of stepwise planarity, presenting a new paradigm for developing high-efficiency red/NIR TADF OLEDs.
13 Feb 15:44
by Mingxin Xing,
Guohao Chen,
Shuni Wang,
Xiaojun Yin,
Jiahui Liu,
Zhuixing Xue,
Nengquan Li,
Jingsheng Miao,
Zhongyan Huang,
Chuluo Yang
By decorating the MR skeleton with alkyl groups, and subsequently a diarylamino group at the para-position of a boron atom, an ideal narrowband pure-blue MR-TADF emitter is developed, and the corresponding OLEDs exhibit state-of-the-art performance with EQEs of up to 33.4 % and a CIEy of 0.046.
Abstract
Developing highly efficient pure-blue organic light-emitting diodes (OLEDs) that meet the stringent BT.2020 standard by using multi-resonance thermally activated delayed fluorescence (MR-TADF) materials has long been a formidable challenge. In this study, a strategy is demonstrated for high-performance blue MR-TADF emitters by gradually decorating the MR framework with alkyl groups, and subsequently introducing a diarylamino group at the para-position of boron atom. The proof-of-concept molecule, IPrBN-mCP, exhibits a narrowband deep-blue emission peaking at 452 nm, with a very narrow full-width at half maximum (FWHM) of 19 nm in solution, and a remarkably high photoluminescence quantum yield (PLQY) approaching unity in doped films. As a result, OLEDs based on IPrBN-mCP achieve not only a high maximum external quantum efficiency (EQEmax) of 33.4% but also ultrapure blue emission with a Commission Internationale de L'Eclairage (CIE) y value of 0.046, fully satisfying the BT.2020 blue standard. This represents the first OLED example fully meeting the rigorous color requirements of the BT.2020 blue standard while simultaneously achieving an EQE exceeding 30%.
12 Feb 14:39
by Ming Zhang,
Dian‐Ming Sun,
Kai Wang,
Jing Chen,
Yin‐Qiong Zhou,
Heng‐Yuan Zhang,
Hao Zhuo,
Zu‐Hong Xiong,
Hui Lin,
Si‐Lu Tao,
Cai‐Jun Zheng,
Xiao‐Hong Zhang
A novel strategy to construct solution-processable exciplex emitters is proposed by utilizing the dendritic oligomer as substrate, simultaneously realizing excellent solution-process adaptability, good dispersibility to restrain intermolecular aggregation-caused quenching, and improved exciton utilization. Impressively, DMAC-DPS:PO-T2T:SimCP3 achieves an external quantum efficiency of 29.7% in solution-processed device, which is comparable with the best results among all solution-processable emitters.
Abstract
Due to the feature of the strong intermolecular interactions causing aggregation-caused excitons quenching (ACQ) of solution process, realizing high-performance solution-processed organic light-emitting diodes (OLEDs) based on thermally activated delayed fluorescence (TADF) emitters remains a formidable challenge nowadays. To address this issue, herein, a novel strategy is proposed to construct solution-processable ternary exciplex emitters by utilizing the dendritic oligomer as the substrate, simultaneously realizing excellent solution-process adaptability, good dispersibility to restrain harmful ACQ, and improved exciton utilization with multiple reverse intersystem crossing channels. Accordingly, dendritic oligomer-based exciplex systems are constructed by combining small-molecule donor and acceptor components with the multi-carbazole-substituted tetraphenylsilane-core analog as substrate. And their film morphologies, photoluminescence quantum yields (ΦPLs), and non-radiative decay rates of triplet excitons (k
nr
Ts) are significantly improved. Among them, DMAC-DPS:PO-T2T:SimCP3 exhibits the highest ΦPL of 97.5% and the lowest k
nr
T of 1.0 × 103 s−1, and realizes the best maximum external quantum efficiency of 29.7% in solution-processed OLED, which is comparable with the highest electroluminescence efficiencies of all solution-processable emitters. Therefore, this work will provide a prospective pathway to develop efficient solution-processable exciplex emitters and promote the progress of solution-processed OLEDs.
12 Feb 14:37
by Min Zhu,
Zhuxia Wu,
Tingting Shi,
Shuang‐Qiao Sun,
Ziming Kuang,
Qi Sun,
Yue‐Min Xie,
Shuit‐Tong Lee,
Man‐Keung Fung
By adopting an efficient pyridine passivator, 5-Bromo-2-fluoropyridine (PD), to inhibit nonradiative recombination in pure red perovskite light-emitting diode (PeLED) units, novel structured hybrid perovskite/organic tandem white light-emitting diodes (POTWLEDs) are developed by integrating bottom red PeLED units with top blue OLED units, which promotes a record EQE of 25.9% for perovskite-based white light-emitting diodes (WLEDs).
Abstract
Perovskite light-emitting diodes (PeLEDs) have recently attracted great interest for their superior electroluminescent properties. However, the development of pure red (620–660 nm) PeLEDs as an essential component for display applications continues to be hampered by severe nonradiative recombination. Particularly, the solution fabrication process of perovskites poses a challenge in the fabrication of white PeLEDs, which further hinders their commercialization. Herein, a novel design is reported of high-efficiency hybrid perovskite/organic tandem white light-emitting diodes (POTWLEDs) by integrating bottom pure red (640 nm) PeLED units with top blue OLED units. To optimize device performance, 5-Bromo-2-fluoropyridine (PD) is introduced, featuring strong electronegative groups of C─N and C─F, as a pyridine passivator into pure red PeLEDs to inhibit nonradiative recombination in the perovskites by passivating defects and improving phase purity of perovskite films, which promotes a maximum external quantum efficiency (EQE) of 20.4%. By integrating the optimized red PeLED units with blue OLED units, efficient POTWLEDs are obtained with high EQE values of 25.9 and 23.7% with CIE coordinates of (0.279 and 0.339) and (0.310 and 0.330), respectively. These values represent the highest efficiencies reported for perovskite-based white light-emitting diodes (WLEDs), illustrating the great potential for solid-state lighting and display applications.
12 Feb 14:33
by Rong‐Rong Gao,
Cheng Chen,
Yan‐Bo Huang,
Xiao‐Ye Wang
Multi-resonance (MR) 1,4-BN-heteroarene has been employed for narrowband photodetectors with a phototransistor configuration for the first time by anchoring narrowband-absorption MR molecules onto a high-mobility indium-zinc-oxide (IZO) semiconductor. Such a device enables excellent photodetection performance and a record-small detecting full-width at half-maximum (FWHM) of 33 nm among intrinsic narrowband absorbing materials.
Abstract
As an emerging class of optoelectronic materials, multi-resonance (MR) 1,4-BN-heteroarenes have been extensively employed as narrowband electroluminescence materials, whereas their absorption feature has largely been neglected. Here we construct the first MR-molecule-based phototransistor for filterless narrowband photodetectors (NBPDs) by anchoring narrowband absorption MR molecules on a high-mobility semiconductor indium-zinc-oxide (IZO) film. The resulting device exhibits high-performance photodetection with a small full-width at half-maximum (FWHM) of 33 nm, which represents a new record for NBPDs based on intrinsic narrowband absorbing materials. These results demonstrate the great potential of MR materials as a new molecular platform for developing high-performance NBPDs.
12 Feb 14:30
by Kaiyuan Zhang,
Xingdong Wang,
Mengyu Wang,
Shumeng Wang,
Lixiang Wang
Electrostatic interaction between a dendritic host (8CzTPS) with a strong positive electrostatic potential (ESP) and a dendritic emitter (D2-DBN) with multiple negative ESP sites was used to induce a high horizontal dipole orientation of 83.0 % for the emitter in solution-processed films. The resulting blue narrowband device realizes an external quantum efficiency of 35.3 % and narrow bandwidth of 17 nm.
Abstract
The multiple resonance thermally activated delayed fluorescence (MR-TADF) device has drawn great attention due to their outstanding efficiency and color purity. However, the efficiency of solution-processed MR-TADF devices is still far behind their vacuum-deposited counterparts, due to the uncontrollable horizontal emitting dipole orientation for emitters during solution process, resulting in low light out-coupling efficiency. Here, we proposed a new strategy namely electrostatic interaction between a dendritic host with high positive electrostatic potential (ESP) and dendritic emitter with multiple negative ESP sites, which could induce high horizontal dipole ratio (Θ||) up to 83.0 % in solution-processed films. For this couple, the largest plane of dendritic host tends to anchor on the substrate, and thus the strong positive electrostatic site mainly lies at the exposed tetraphenylsilicon, which could electrostatically attract the multiple negative electrostatic sites of the dendritic emitter, realizing horizontal dipole orientation. Moreover, the highly twisted structure of dendritic host and dendron encapsulation of emitter could effectively suppress aggregation, leading a high photoluminescence quantum yield of 98.6 %. As a result, the solution-processed blue MR-TADF devices exhibit a record-break external quantum efficiency of 35.3 %, as well as narrow bandwidth of 17 nm and pure blue color with CIE coordinates of (0.137, 0.176).
12 Feb 14:29
by Zhihai Yang,
Denghui Liu,
Xiangyi Cheng,
Tong Wang,
Zhizhi Li,
Guo-Xi Yang,
Zijian Chen,
Juntao Hu,
Yu Fu,
Xuewei Nie,
Yongxia Ren,
Yitong Zeng,
Yuling Chen,
Kunkun Liu,
Mengke Li,
Shi-Jian Su
Chalcogen-containing carbonyl groups have been incorporated into fused organoboron multiple resonance emitters. 2TXBN and BNTXBN exhibit bright orange-red emissions with maxima at 582 and 585 nm, respectively, along with narrow full widths at half maximum of 30 and 32 nm. Furthermore, the nonbonding orbital of 2TXBN delocalizes within the thioxanthone segment, which raises the first triplet energy level and reduces the singlet-triplet energy gap.
Abstract
Chalcogen-containing carbonyls, specifically thioxanthone (TX), hold great potential in organic light-emitting diodes (OLEDs). While the development of narrowband OLEDs with chalcogen-containing carbonyls remains challenging due to difficulties in achieving both high device efficiency and narrow emission spectra. Herein, via a strategic incorporation of the TX moiety, two orange-red narrowband emitters, 2TXBN and BNTXBN, are designed and synthesized for the first time. Both 2TXBN and BNTXBN exhibit bright orange-red emissions with peaks at 582 and 585 nm, respectively, along with narrow full widths at half maxima of 30 and 32 nm. Notably, 2TXBN demonstrates delocalization of the nonbonding orbital within the TX segment, which raises the first triplet energy level and reduces the singlet-triplet energy gap. This electronic structural adjustment effectively shortens the delayed fluorescence lifetime, leading to enhanced device performance. Accordingly, OLED employing 2TXBN as the emitter achieves remarkable performance, with a maximum external quantum efficiency of 31.0 %, a current efficiency of 69.0 cd A−1, and a power efficiency of 76.0 lm W−1, highlighting the efficacy of the nonbonding orbital delocalization strategy in achieving bathochromic-shifted narrowband OLED materials.
12 Feb 14:29
by Xuan Zeng,
Xiaofeng Luo,
Guoyun Meng,
Xuewen Wang,
Dongdong Zhang,
Lian Duan
Sym- and asym-expanded heterohelicene isomers were developed by one-pot borylation synthesis, which exhibit narrowband deep-blue emission with record-setting FWHM of 18 nm and near-unity photoluminescence quantum yield. Corresponding OLED showed superb performance with external quantum efficiency up to 25 % and small efficiency roll-off even at high luminance of 10, 000 cd m−2.
Abstract
Expanded heterohelicenes composed of alternating linearly and angularly fused multi-resonance (MR) skeletons have gained wide interest owing to their promising narrowband emissions. Herein, a pair of sym- and asym-expanded heterohelicene isomers was obtained by merging boron/oxygen (B/O)-embedded MR triangulene and indolo[3,2,1-jk]carbazole units via one-pot synthesis. Owing to their fully resonating extended helical skeleton, the target heterohelicenes exhibit a significantly narrowed spectra bandwidth while emission red-shifting, thus affording deep-blue narrowband emission with a peak at approximately 460 nm, full-width-at-half-maximum (FWHM) of only 18 nm, and near-unity photoluminescence quantum yields. In comparison to the symmetrical structure, the asym-expanded heterohelicene displays suppressed aggregation within doped films, thereby showing superior narrowband electroluminescence in devices with CIE coordinates of (0.12, 0.18) and a high external quantum efficiency of up to 25 %, which retains 18.1 % even at a high luminance of 10,000 cd m−1. Overall, this work provides a novel paradigm for the development of narrowband expanded heterohelicenes.
12 Feb 14:24
by Yixin Wu,
Manli Huang,
Lin Cheng,
Junyao Zhang,
Yi Pan,
Shek-Man Yiu,
Kai Chung Lau,
Jie Yan,
Chuluo Yang,
Yun Chi
Blue hyper-OLED devices using the Ir(III) emitter
m
-ct16 as the dopant sensitizer at 30 wt % and ν-DABNA as the terminal emitter at 1 (2) wt % afforded blue emission with a narrowband peak maximum at 471 (472) nm, CIEy of 0.157 (0.149), EQE1000 of 32.1 (28.4) %, and J
90 of 15.0 (31.0) mA ⋅ cm−2, setting a new record of Figure of merit (FOM) and showing minimal quenching at high current density.
Abstract
Ir(III) complexes are particularly noted for their excellent photophysical properties in giving blue OLED phosphors. In this study, two distinctive carbene pro-chelates LAH2
+ and LBH2
+ (or LCH2
+) were employed in preparation of heteroleptic Ir(III) complexes, to which LAH2
+ bears a cyano substituted benzoimidazolium along with N-mesityl appendage, while LBH2
+ (or LCH2
+) carries the symmetrical benzoimidazolium entity. Notably, the reversible equilibration at high temperature was observed for
m
,
f
-ct14 and
m
,
f
-ct15 with a single LA chelate. In contrast, only the mer-substituted
m
-ct16 was obtained upon employing two LA chelates. All Ir(III) complexes exhibited blue photoluminescence (Φ
PL
≥
${\ge }$
78 %) with short radiative lifetimes (τrad
≤
${\le }$
1.05 μs) in solution. The Ph OLED device with
m
-ct16 afforded an external quantum efficiency (EQE) of 22.8 % at 5000 cd ⋅ m−2. Moreover, the hyper-OLED based on
m
-ct16 and v-DABNA exhibited EQE1000 of 32.1 % (EQE recorded at 1000 cd ⋅ m−2) and J
90 of 15.0 mA cm−2 (current density at 90 % of max. EQE). Its suppressed efficiency roll-off (EQE of 32.1 % and 27.7 % at 1000 cd ⋅ m−2 and 10000 cd ⋅ m−2) demonstrated a milestone in fabrication of blue OLED devices.
12 Feb 14:23
by Yongqiang Zhang,
Yue Liu,
Xueyan Ren,
Yihong Kang,
Shurong Ding,
Siyu Lu
We have developed a convenient strategy to achieve TDAC CDs that cover the entire visible region. By optimizing the doping level of Pyr-CDs and embedding them in different rigid matrices, we can effectively tailor various color variations of the afterglow within the visible region. The successful utilization of 4D coding technique for multimodal anti-counterfeiting and advanced dynamic information encryption promotes the practical applications of afterglow materials.
Abstract
Time-dependent afterglow colored (TDAC) behavior differs from static afterglow by involving wavelength changes, enabling low-cost, high-level encryption and anti-counterfeiting. However, the existing carbon dot (CD)-based TDAC materials lack a clear mechanistic explanation and controllable wavelength changes, significantly hindering the progress of practical applications in this field. In this study, we synthesized CDs composites with customizable tunable TDAC wavelengths across the visible region. Furthermore, we elucidated the underlying mechanism of TDAC that exhibits sequential weakening and relative strengthening of long- and short-wavelength afterglow centers. This phenomenon arises due to strong emission with a short lifetime originating from long-wavelength thermally activated delayed fluorescence (TADF), along with weak emission having a longer lifetime originating from short-wavelength phosphorescence. The presence of surface-rich carboxyl groups on CDs determines the short-wavelength afterglow in their dispersed state while their high conjugation degree governs the long-wavelength afterglow in their aggregated state. Additionally, appropriate doping levels of CDs enhance color change phenomena during afterglow. Finally, by embedding CDs into different rigid matrix, the range of afterglow changes can be tailored arbitrarily within the visible light region. Leveraging these exceptional TDAC characteristics has allowed us to successfully develop advanced 4D coding technologies that facilitate multi-mode anti-counterfeiting and dynamic information encryption.
12 Feb 14:23
by Pengxing He,
Jingyao Ye,
Junrui Zhang,
Taige Lu,
Wenying Cui,
Junyang Liu,
Chengshuo Shen,
Wenjing Hong,
Xunshan Liu
Investigation of charge transport behaviors in Helicene-based molecular wires under alternating currents of varying frequencies.
Abstract
Despite extensive studies has been explored on single-molecule switches and rectifiers, the design of single-molecule inductors has not been explored due to the experimental challenges in the investigation of frequency-dependent charge transport at the single-molecule scale. In this study, we synthesized a helicene-based helical molecular wire and carried out meticulous single-molecule conductance measurements, combined with current–voltage (IV) studies with varying frequencies using the scanning tunneling microscope break junction (STM-BJ) technique. Our results reveal the formation of a single-molecule junction and highlight the unique behavior of the molecular wire in response to different alternating current (AC) varying frequencies. The transport of charges occurs selectively either through the coiled backbone of the conjugated helical structure or vertically via π–π stacking, depending on the frequency of the applied AC. Notably, our investigation demonstrates the functionality of the wire as an inductor at low frequencies, and a capacitor at high frequencies. This work lays the foundation for a systematic approach to designing, fabricating, and implementing single-molecule logic devices such as inductors and wave filters.
12 Feb 14:21
by Zhong-Hao Wang,
Chen-Hui Liu,
Hui-Li Sun,
Lin Zheng,
Mei Pan
Hot exciton fluorescence and long afterglow emission were realized in the complexes by supramolecular self-assembly strategy. The complexes emitted bright afterglow after excited by 365 nm, 450 nm, white LED and even 800 nm near-infrared laser under atmospheric conditions.
Abstract
Metal-organic complexes with long afterglow luminescence have attracted extensive attention due to potential applications in display, sensing and information security. However, most of the metal-organic complex long afterglow materials reported so far are limited to the use of UV light as the excitation source, and the ambiguity of the structure-activity relationship makes the development of metal-organic complexes extremely limited. Herein, a series of metal-organic complexes with ultralong emission lifetime is constructed by coordination assembly of Zn(II) with three isomers. These complexes can emit afterglow when excited by UV light, blue LED, cell phone flashlight or even near-infrared light (800 nm) under ambient conditions, and the afterglow is also observed at 360 K. More interestingly, the inactivation pathway of the triplet exciton was altered by the strategy of supramolecular self-assembly, which leads to these complexes having hot exciton fluorescence (HEF) emission that is not present in the ligand. The relationship between structure and optical properties is investigated in detail by experiments and theoretical calculations. This work provides guidance for studying the modulation of optical properties by coordination interactions.
12 Feb 14:16
by Lin-Tao Bao,
Rui-Hua Zhang,
Xiaoyue Yuan,
Xueli Wang,
Peicong Wu,
Xu-Qing Wang,
Jinquan Chen,
Anwei Zhu,
Hai-Bo Yang,
Wei Wang
A new family of pyrenophanes with rigidly locked pyrene dimers and varied bridges has been designed and synthesized. These compounds reveal intense and stable circularly polarized photoluminescence (CP-PL) and electrochemiluminescence (CP-ECL), thus making them attractive platforms for both fundamental investigations on pyrene excimers and practical applications, such as chiral sensing.
Abstract
Aiming at the construction of novel platforms with excellent performances in both circularly polarized photoluminescence (CP-PL) and electrochemiluminescence (CP-ECL), a new family of pyrenophanes with rigidly locked pyrene dimers and varied bridges has been designed and synthesized. Attributed to densely packed pyrene excimers, the resultant pyrenophanes revealed tunable bridge-dependent emission behaviors, as investigated by femtosecond time-resolved transient absorption spectroscopy. More importantly, all these planar chiral pyrenophanes display strong CP-PL with large dissymmetry factor (g
PL) values up to 0.034, and such excellent performances remain stable in a wide range of solvents, temperatures, and concentrations. Attractively, the highest g
ECL values up to 0.014 reported so far has been achieved for the CP-ECL emissions of the chiral pyrenophanes. Attributed to their unique structural features and outstanding CPL performances, these novel pyrenophanes could serve as promising platforms for both fundamental investigations on pyrene excimers and practical applications such as chiral sensing.
12 Feb 14:12
by Meng Li,
Chao Feng,
Ke Zhang,
Bianxiang Zhang,
Liheng Feng,
Lei He,
Chuan-Feng Chen
A pair of chiral thermally activated delayed fluorescence (TADF) imidazolium compounds are synthesized by attaching imidazolium hexafluorophosphate to an axially chiral TADF framework. The chiral imidazolium salts showed small ΔE
ST, high PLQY, strong CPL and excellent redox properties. Moreover, circularly polarized light-emitting electrochemical cells (CP-LECs) prepared with this compound, without additional ionic liquids, exhibit CPEL signals with |g
EL| of 3.3×10−3 and EQEmax of 5.2 %.
Abstract
A pair of axially chiral thermally activated delayed fluorescent (TADF) enantiomers, R-TCBN-ImEtPF6
and S-TCBN-ImEtPF6
, with intrinsic ionic characteristics were efficiently synthesized by introducing imidazolium hexafluorophosphate to chiral TADF unit. The TADF imidazolium salts exhibited a high photoluminescence quantum yield (PLQY) of up to 92 %, a small singlet–triplet energy gap (▵E
ST) of 0.04 eV, as well as reversible redox properties. Furthermore, the enantiomers showed distinct mirror-image CD and CPL activities with g
lum values of −3.7×10−3 and +3.4×10−3. Notably, by doping the axial TADF imidazolium salts into achiral TADF sensitizer, sandwich-structured light-emitting electrochemical cells (LECs) without the addition of ionic liquids (ILs) or ionic transition-metal compounds (iTMCs) were fabricated. When driven at 50 A m−2, the LECs displayed an EQE of up to 5.2 % and strong circularly polarized electroluminescence (CPEL) with g
EL values of +3.3×10−3 and −3.0×10−3. This represents the first CP-LEC based on TADF materials and offers a promising strategy for the development of high-performance CPEL devices.
12 Feb 14:03
by Zhuixing Xue,
Yuxuan Hu,
Shengbing Xiao,
Jiahui Liu,
Jingsheng Miao,
Chuluo Yang
Ultra-narrow green multi-resonance thermally activated delayed fluorescence emitters have been developed by synergistic cyano-decoration and a π-extension strategy. The resulting organic light-emitting diodes deliver an exceptional green color purity that approaches the BT.2020 standard, as well as high external quantum efficiencies exceeding 30 %.
Abstract
The development of pure-green organic emitters with ideal emission peaks and ultra-narrow full-widths at half-maximum (FWHMs) remains a formidable challenge. Herein, we report two new green emitters, CNBN and MCNBN, which achieve extremely narrow FWHMs by synergistic rigid π-extension and cyano-substitution of a sky-blue multi-resonance thermally activated delayed fluorescence (MR-TADF) core. The introduction of cyano groups induces red-shifts in the emission to the green region and dramatically minimizes the FWHMs. In toluene solution, CNBN and MCNBN exhibit narrowband emission with a maximum at 501 nm and 510 nm with ultra-narrow FWHMs of 14 nm/0.066 eV and 15 nm/0.071 eV, respectively. Given the near-unity photoluminescence quantum yields and almost 100 % horizontal dipole orientation, the electroluminescent (EL) devices based on CNBN and MCNBN deliver external quantum efficiencies (EQEs) exceeding 30 % with FWHMs of 16 nm/0.072 eV and 17 nm/0.080 eV, respectively. Notably, the MCNBN-based device achieves pure-green emission with a maximum at 517 nm with Commission Internationale de l’Éclairage coordinates of (0.17, 0.74), closely aligning with the BT.2020 green standard.
12 Feb 09:11
by Maoqiu Li,
Lei Hua,
Jinyang Zhao,
Yuchao Liu,
Shouke Yan,
Zhongjie Ren
A series of rigid orange-red emitters with “U”-shaped, folded “Z”-shaped and “W”-shaped configurations have been constructed. The excited state and photophysical properties of the emitters can be effectively regulated by changing the three-dimensional architectures. Organic light-emitting diodes (OLEDs) based on QX36 exhibit a maximum external quantum efficiency of up to 32.3 %, the highest for solution-processed orange-red OLEDs.
Abstract
Achieving efficient long-wavelength organic light-emitting diodes (OLEDs) remains a challenge due to the energy gap law, which leads to increased non-radiative decay rates as the emission wavelength shifts to longer regions. Herein, a strategy of constructing folded three-dimensional architectures is proposed to explore new orange-red thermally activated delayed fluorescence (TADF) emitters with through-space charge transfer characteristics. Innovatively, naphthalene is selected as a bridge to connect O-bridged triphenylamine donor and planar dibenzo[a,c]phenazine acceptor respectively via simple Suzuki–Miyaura Coupling. In this way, a series of rigid orange-red emitters with “U”-shaped, folded “Z”-shaped and “W”-shaped configurations are elaborately constructed by modifying end groups, adjusting the numbers of naphthalene and donor, and regulating the linkage sites. The excited state natures and photophysical properties of the emitters can be effectively regulated and optimized by changing three-dimensional architectures. Finally, the prepared emitter QX36 achieves a lower non-radiative transition rate, a higher radiative rate and a higher photoluminescence quantum efficiency. Solution-processed OLEDs based QX36 present the excellent electroluminescent performance with a maximum external quantum efficiency (EQE) of up to 32.3 % and EQE of 20.6 % at 1000 cd m−2, which are the leading values of solution-processed orange-red OLEDs. This work demonstrates the promising potential of folded TADF based naphthalene backbone as emitters for future efficient solution-processed long-wavelength OLEDs.
12 Feb 08:40
by Hao Sun, Xuping Li, Chao-Hsien Hsu, Chieh-Ming Hung, Bin Wu, Zhe-Hong Su, Glib V. Baryshnikov, Chenzi Li, Hans Ågren, Zhiyun Zhang, Wei Huang, Dayu Wu, Pi-Tai Chou, and Liangliang Zhu
Journal of the American Chemical Society
DOI: 10.1021/jacs.4c18235
17 Jan 09:25
by Xueli Wang,
Jie Zhou,
Mingkang Wang,
Yuze Wang,
Zhetao Shen,
Haitao Sun,
Zhubin Hu,
Xiao Luo,
Youjun Yang,
Jinquan Chen
Proximal oblique-packed (V-shaped packing) of heptamethine cyanine dimer can induce multi-channel ultrafast triplet state generation with the rate constants up to ~1011 s−1, leading a triplet state quantum yield of 18.9 % upon excitation at 750 nm, which is almost an order of magnitude higher than that of the monomer (IR780, 2.1 %).
Abstract
Near-infrared (NIR) triplet dyes are the cornerstones of cutting-edge biomedical and material applications. The difficulty in rational development of triplet dyes increases exponentially as the absorption wavelength shifts deeper into the NIR range. Although classical H-/J-typed packing of NIR dyes has the potential to enhance intersystem crossing (ISC) compared with that in single-chromophore dyes, the triplet state quantum yields remain limited in such strategy. Herein, proximal oblique-packed (V-shaped) heptamethine cyanines (SZ780) through spiro-connection were achieved. Multi-channel ultrafast ISC were direct observed in SZ780 and a record high ISC rate constant (up to ~1011 s−1) is registered among all the reported NIR triplet dyes. SZ780 exhibits a triplet state quantum yield of 18.9 % upon excitation at 750 nm, which is almost an order of magnitude higher than that of the monomer (IR780, 2.1 %) and nearly threefold increase compared to that of the H-packed dimer (SC780) (6.7 %). Moreover, SZ780 efficiently generates singlet oxygen under 808 nm light irradiation, inducing cancer cell apoptosis in vivo. These findings demonstrate that constructing V-aggregated dyes system by spiro-connection offers a powerful approach for the design of high-performance NIR triplet sensitizers.
17 Jan 09:13
by Shiping Yang, Qian Jia, Xinwen Ou, Fang Sun, Chaoqi Song, Tingxing Zhao, Ryan T. K. Kwok, Jianwei Sun, Zheng Zhao, Jacky W. Y. Lam, Zhongliang Wang, and Ben Zhong Tang
Journal of the American Chemical Society
DOI: 10.1021/jacs.4c15216