近年来,由于具有发光波长可调、光色纯度高、材料制备成本低等优势,有机无机卤化物钙钛矿发光二极管的研究取得了长足的发展.通常来说,为了制备性能优异的钙钛矿发光二极管,需要同时兼顾发光层的高量子转化效率、平衡的载流子注入和良...近年来,由于具有发光波长可调、光色纯度高、材料制备成本低等优势,有机无机卤化物钙钛矿发光二极管的研究取得了长足的发展.通常来说,为了制备性能优异的钙钛矿发光二极管,需要同时兼顾发光层的高量子转化效率、平衡的载流子注入和良好的光提取效率这三个方面.目前,研究者已经发展出了多种化学钝化方法以提高钙钛矿发光层的量子转化效率.但是在载流子注入方面存在一对矛盾,即在较高的载流子注入密度下,由于俄歇效应,发光层的辐射发光效率不高.因此,高亮度和高量子转化效率很难共存.因此,本文尝试通过调节钙钛矿费米面去调控钙钛矿和电子注入层的异质结,降低电子注入的势垒高度;利用分子掺杂改善空穴注入层的空穴传输迁移率,最终实现器件的平衡且高效的电荷注入.通过一系列的电荷注入调控和优化,该工作实现了同时具有较高亮度和较高发光效率的绿光钙钛矿发光二极管.最优器件在2.65 V,115 mA cm^-2的工作状态下取得了55000 cd m^-2的发光亮度和8.0%的转化效率.同时在100 m A cm^-2的恒定注入电流下,器件转化效率降低到初始的50%时的寿命达到了160 min,显示了电荷注入调控对器件稳定性提升的重要影响.展开更多
The development of organic materials with white-light emission and thermally activated delayed fluorescence(TADF)properties in the solid state remain a challenge.Herein,a series of white-light-emitting organic luminog...The development of organic materials with white-light emission and thermally activated delayed fluorescence(TADF)properties in the solid state remain a challenge.Herein,a series of white-light-emitting organic luminogens have been developed and are found to show aggregation-induced delayed fluorescence(AIDF)characteristics.The AIDF emitters present dual-emission consisted of prompt fluorescence and TADF in the crystalline state.Their white-light emissions can be easily tuned by altering the chemical structure and connecting position of the heterocyclic aromatic substituent.Under the stimuli of mechanical force and solvent vapor,the compounds exhibit remarkable and reversible mechanochromism,in which their emission colors are switchable between white and yellow.Upon grinding,they also display linearly tunable luminescence colors,as well as force-induced TADF enhancement,which may be associated with the more compact molecular packing and the restriction of intramolecular motions.The results from time-resolved emission scanning and theoretical calculation suggest that the dual-emission of the AIDF luminogens likely results from the twisted intramolecular charge transfer transitions of the molecules,and the reversible mechanochromism properties probably stem from the interconversion of the quasi-axial and the quasi-equatorial conformations.展开更多
基金in part supported by Research Grants Council of Hong Kong,particularly,via Grant Nos.Ao E/P-03/08,T23-407/13-N,Ao E/P-02/12,14207515,14204616CUHK Group Research Scheme,and ITS/088/17 by Innovation and Technology Commission,Hong Kong SAR Governmentthe National Natural Science Foundation of China for the support,particularly,via Grant No.61229401。
文摘近年来,由于具有发光波长可调、光色纯度高、材料制备成本低等优势,有机无机卤化物钙钛矿发光二极管的研究取得了长足的发展.通常来说,为了制备性能优异的钙钛矿发光二极管,需要同时兼顾发光层的高量子转化效率、平衡的载流子注入和良好的光提取效率这三个方面.目前,研究者已经发展出了多种化学钝化方法以提高钙钛矿发光层的量子转化效率.但是在载流子注入方面存在一对矛盾,即在较高的载流子注入密度下,由于俄歇效应,发光层的辐射发光效率不高.因此,高亮度和高量子转化效率很难共存.因此,本文尝试通过调节钙钛矿费米面去调控钙钛矿和电子注入层的异质结,降低电子注入的势垒高度;利用分子掺杂改善空穴注入层的空穴传输迁移率,最终实现器件的平衡且高效的电荷注入.通过一系列的电荷注入调控和优化,该工作实现了同时具有较高亮度和较高发光效率的绿光钙钛矿发光二极管.最优器件在2.65 V,115 mA cm^-2的工作状态下取得了55000 cd m^-2的发光亮度和8.0%的转化效率.同时在100 m A cm^-2的恒定注入电流下,器件转化效率降低到初始的50%时的寿命达到了160 min,显示了电荷注入调控对器件稳定性提升的重要影响.
基金supported by the National Natural Science Foundation of China(No.51603233)the Natural Science Foundation of Guangdong Province of China(Nos.2019A1515010550,2020A1515010439,2019A1515011389)the GDUPS(2019)the Opening Foundation of Key Laboratory for Polymeric Composite and Functional Materials of Ministry of Education(Sun Yat-sen University,No.PCFM-2019-05)。
文摘The development of organic materials with white-light emission and thermally activated delayed fluorescence(TADF)properties in the solid state remain a challenge.Herein,a series of white-light-emitting organic luminogens have been developed and are found to show aggregation-induced delayed fluorescence(AIDF)characteristics.The AIDF emitters present dual-emission consisted of prompt fluorescence and TADF in the crystalline state.Their white-light emissions can be easily tuned by altering the chemical structure and connecting position of the heterocyclic aromatic substituent.Under the stimuli of mechanical force and solvent vapor,the compounds exhibit remarkable and reversible mechanochromism,in which their emission colors are switchable between white and yellow.Upon grinding,they also display linearly tunable luminescence colors,as well as force-induced TADF enhancement,which may be associated with the more compact molecular packing and the restriction of intramolecular motions.The results from time-resolved emission scanning and theoretical calculation suggest that the dual-emission of the AIDF luminogens likely results from the twisted intramolecular charge transfer transitions of the molecules,and the reversible mechanochromism properties probably stem from the interconversion of the quasi-axial and the quasi-equatorial conformations.
