光与时间魔法的奇妙碰撞——追寻长余辉寿命的足迹

发光寿命是光化学的重要概念,也是体现发光材料性质的一项重要参数。尽管发光材料在人类生产生活、军事及航空航天领域有广泛的应用,但是普通大众对于“发光寿命有长有短”这一科学概念并没有清晰的认识。本项目以生活中的光为切入点,以发光寿命在人眼可识别范围内(>100 ms)的长余辉材料作为展示媒介。通过探究三聚氰胺与苯二甲酸在水介质中的自组装,设计并合成了一类寿命长、亮度高的有机长余辉材料,因其合成方法简单、原料便宜易得、实验现象明显且重现性高,非常适合作为科普主题;同时在日常生活中探寻发光现象,创新设计趣味动画、“光绘涂鸦”等新型科普模式,寓教于乐、寓教于做,点燃人们探究化学世界的热情;借助Bilibili、抖音等网络平台广泛宣传,拓宽化学知识的普及范围。针对具有不同年龄和知识结构对象群体的特点和需求,科普内容设立了多个独立互动模块,“量体裁衣”,力求获得“覆盖面广、接受度高”的效果,让发光寿命真正贴近生活、走向大众。

1,2-二咔唑基-4-溴苯的合成及长余辉性质表征

有机功能材料是有机化学重要的研究方向之一。将国际前沿的先进有机功能材料合成方法及其性质表征引入到基础有机化学实验,有望进一步丰富教学内容,促进本科教学与科研成果之间的衔接。基于此目的,本项目选择有机长余辉材料这一国际前沿研究热点,与芳香亲核取代反应实验教学相结合,指导学生认识合成反应在构建有机功能材料中的关键作用,进一步将知识体系延伸至现代波谱技术,树立学生正确的科学观念。通过本项目,形成“有机反应-分子结构-材料功能”为链条的系统教学,培养学生的科学素养和综合创新能力。

芳香亲核取代反应合成4,4’-双(3,6-二叔丁基咔唑基)二苯甲酮及其结构和热活化延迟荧光性质表征

有机功能材料的制备已经成为现代有机化学的重要研究方向之一,并逐步形成了与其相关的中间体和终产物合成产业链。目前,基础有机化学实验主要涵盖单元操作和简单精细化学品合成。将国际前沿的先进有机功能材料合成方法及其性质表征引入到基础有机化学实验,有望进一步扩展教学内容,促进课程与新兴产业之间的衔接。基于此目的,本项目选择有机热活化延迟荧光材料这一有机发光材料的国际前沿热点,将材料合成与有机单元反应教学相结合,丰富有机反应教学手段的同时,指导学生认识合成反应在构建有机功能材料中的关键作用,进一步将知识体系延伸至现代荧光光谱技术,展示有机化合物结构与有机功能材料性质之间的科学联系,从而完成对“合成–分子结构–材料功能”这一知识链条的系统教学。通过本项目,学生不仅可以强化基础实验操作,完成传统有机化学实验学习,而且可以掌握核磁共振谱及荧光光谱技术,让学生体验完整的科研过程,形成有梯度、复合型的知识体系。

Overcoming power efficiency limitation of white fluorescence light-emitting diodes via multilevel-hydrogen-bond matrix

High power efficiency and low efficiency roll-off at practical luminance are two requirements for new-generation energy-saving lighting technologies,which are still bottlenecks of thermally activated delayed fluorescence(TADF)white organic light-emitting diodes(WOLED),despite the advantages of TADF materials and devices in low cost and high sustainability.Herein,we developed a spiro phosphine oxide host named SSOXSPO,which can form multiple and multidirectional intermolecular hydrogen bonds(IHB).The resulted multilevel IHB network integrates long-range ordered and short-range disordered alignments for suppressing triplet-polaron quenching(TPQ)and triplet-triplet annihilation(TTA).Electronic characteristics of SSOXSPO matrix are further regulated,leading to the optimal exciton allocation through balancing energy and charge transfer.As consequence,using SSOXSPO as host,the single-emissive-layer TADF WOLEDs realized the record performance,including ultralow operation voltage as∼4.0 V,power efficiency beyond fluorescent tube(70.1 lm W−1)and negligible external quantum efficiency roll-off(3%)at 1000 nits for indoor lighting.This work demonstrates that multiple interplays supported by host matrixes in TADF WOLEDs can facilitate the synergistic effects of TADF emitters on 100%exciton utilization.

White Fluorescent Organic Light-Emitting Diodes with 100%Power Conversion

Energy-efficient lighting sources are desired to provide another solution of carbon emission reduction.White organic light-emitting diodes are promising,because of theoretical internal quantum efficiencies for 100%electric-to-light conversion.However,pure organic fluorescent materials still face a challenge in harvesting triplet excitons for radiation.Herein,we report a white fluorescent organic light-emitting diode having an external quantum efficiency of 30.7%and a power efficiency of 120.2 Im w^(-1).In the single emissive layers,we use blue thermally activated delayed fluorescent emitters to sensitize a yellow fluorescent emitter.Transient photoluminescence and electroluminescence analyses suggest that a blue thermally activated delayed fluorescent molecule with~100%reverse intersystem crossing efficiency and negligible triplet nonradiative rate constant completely converts triplet to singlet,suppressing triplet quenching by a yellow fluorescent emitter and ensuring 100%power conversion.

Sky Blue and Yellow Cluster Light-Emitting Diodes Based on Asymmetric Cu_(4)l_(4) Nanocubes

Controllably optimizing excited-state characteristics is crucial for luminescent nanoclusters but remains a formidable challenge.Herein,we report an effective"ligand-induced asymmetrization"strategy for constructing thermally activated delayed fluorescence-featured cubic Cu4l4 nanoclusters with asymmetric configurations,named[tBCzDBFDP]_(2)Cu_(4)l_(4) and[PTZDBFDP]_(2)Cu_(4)l_(4).Through changing 3,6-di-tert-butyl-carbazole(tBCz)to phenothiazine(PTZ)with a stronger electron-donating effect,emission color is tuned from greenish blue of[tBCzDBFDP]_(2)Cu_(4)l_(4) to yellow of[PTZDBFDP]_(2)Cu_(4)l_(4),as well as the triplet locally excited state of the former to the triplet charge transfer state of the latter.Temperature-correlated spectroscopic investigation indicates that in terms of triplet quenching suppression,[tBCzDBFDP]_(2)Cu_(4)l_(4) is superior to[PTZDBFDP]_(2)Cu_(4)l_(4),in accord with the stabilities of their triplet locally excited state and triplet charge transfer state.As a consequence,these asymmetric Cu4l4 nanocubes endowed their cluster light-emitting diodes with the external quantum efficiencies beyond 12%for sky blue and 8%for yellow.These results suggest the significance and effectiveness of ligand engineering for optoelectronic nanoclusters.

膦基电致发光材料及器件的研究进展

芳香膦(氧)基团具有可打断共轭、电子效应适中、位阻大、便于多功能修饰和配位能力强等特点,是少数几个兼具多种功能的基团之一.通过综合运用这些功能,芳香膦(氧)基团在选择性调节分子光电特性等方面显示出了独特的优势.因此,芳香膦(氧)基团不仅适于构建综合性能优异的光电功能材料,进而实现高效的有机电致发光器件,而且能够为选择性研究单一性质变化对材料光电性能的影响提供平台.近年来,膦基光电功能材料逐渐发展成为有机电致发光(organic light-emitting diode, OLED)领域的热点之一,其所展现出的优异性能和清晰的构效关系在丰富OLED材料库、明确材料设计和优化途径,乃至推动OLED技术创新等方面具有重要的理论意义和实际应用价值.我们在膦基电致发光材料及其器件方面开展了比较系统的研究.从材料的设计策略出发,分别开发了膦基主体材料、发光材料和电子传输材料,对这类材料的光物理性质、激发态特性、电学性能以及电致发光器件性能等进行深入研究.本文对这些工作进行了较为系统的总结,以期为今后膦基光电功能材料的开发提供借鉴和参考.

Synergetic Insulation and Induction Effects Selectively Optimize Multiresonancee Thermally Activated Delayed Fluorescence

Multiresonance(MR)emitters featuring narrowband emissions and theoretically 100%exciton harvesting are great potential for organic light-emitting diode(OLED)applications.However,how to functionalize MR molecules without scarifying emission color purity is still a key challenge.Herein,we report a feasible strategy for selective optimization of MR molecules,which is demonstrated by a blue MR emitter tCBNDASPO substituted with a diphenylphosphine oxide(DPPO)group.Compared to its DPPO-free parent molecule,tCBNDASPO preserves narrowband feature with full widths at half maximum(FWHM)values of 28 nm in film and 32 nm in OLEDs and achieves 40%increased photoluminescence(92%)and electroluminescence quantum efficiencies(28%).It is showed that insulation effect of P=O effectively confines the singlet excited state on MR core to keep emission color purity,and its induction effect enhances singlet radiation and triplet-to-singlet conversion.This synergism for selective optimization is based on rational linkage between MR core and functional groups.