节点文献
基于吸热延迟荧光机制的高效有机电致发光器件的研究
Research on High-efficiency Organic Light Emitting Diodes Based on Thermally Activated Delayed Fluorescence
【作者】 张明；
【导师】 郑才俊；
【作者基本信息】 电子科技大学 ， 工程硕士（专业学位）， 2018， 硕士
【摘要】 近几年,基于热激活延迟荧光（TADF）机制的有机电致发光器件备受人们的广泛关注,有望成为下一代信息显示和照明领域的主流技术。然而由于TADF机制在有机电致发光器件领域中的应用尚处于起步阶段,基于热激活延迟荧光材料制备的有机电致发光器件在内部工作机制及实际应用上仍存在着一系列关键的科学问题亟待解决。本文针对以上关键性科学问题展开研究,取得了如下研究成果。1.设计了以CDBP:PO-T2T激基复合物为主体,2CzPN和AnbTPA为发光材料的全荧光的高效TADF有机电致白光器件。通过调节发光层中的载流子传输平衡和激子分配,获得了器件结构最优的白光器件。该白光器件不但实现了高效的电致发光(最大电流效率,功率效率,外量子效率分别为36.7 cdA-1、46.2 lmW-1、19.2%,并且获得了高质量的白光发射。在1000 cdm-2的亮度下,白光的色坐标（CIE）为（0.33,0.38）,显色指数为82,并且在100-3000 cdm-2亮度区间内,色坐标的变化量仅为（0.00,0.02）。其性能表现处于同类型报道的基于TADF机制的有机电致白光器件的领先水平。2.针对高效的红光TADF激基复合物难以获得这一问题,提出了一种引入磷光分子作为组分构建高效红光TADF激基复合物的新策略。磷光分子中的重金属（Ir,Pt）原子具有自旋轨道耦合作用,可以抑制单三重态的非辐射跃迁,从而减少了激子损耗。基于新型激基复合物PO-T2T:Ir（ppy）3为发光材料的有机电致发光器件呈现了波峰位置604 nm,CIE为（0.55,0.44）,最大外量子效率为5%及较长器件寿命的红光发射。其器件性能明显优于基于传统红光激基复合物的有机电致发光器件,证实了我们用磷光分子构建高效红光TADF激基复合物的优势。3.针对基于TADF激基复合物的有机电致发光器件效率较低且效率滚降严重的问题,提出了构建新型三元材料体系激基复合物的设计策略。新型的三元TADF激基复合物具有三个逆系间窜越过程,可以有效的提高三重态激子的利用率。基于此,我们发展了一个高效的三元激基复合物体系CDBP:PO-T2T:DBT-spiro。基于CDBP:PO-T2T:DBT-spiro的有机电致发光器件呈现了2.4 V极低的开启电压和20.5%的极高最大外量子效率,并且在1000 cdm-2的亮度下外量子效率仍然为14.2%。其性能指标居于文献报道的同类型TADF激基复合物器件中的领先水平。
【Abstract】 Recently,novel fluorescent emitters with thermally activated delayed fluorescence（TADF）characteristics based on organic light emitting diodes（OLEDs）have attracted remarkable attention,promising to be the mainstream technology in the next generation of information display and lighting.However,the practical application of TADF mechanism based on OLEDs is in its infancy,there are still lots of key scientific problems about the application of TADF materials and internal energy transfer mechanism of OLEDs to be solved.In this work,we have focused on these key scientific issues and made some achievements listed as below:1.A full-fluorescence high-efficiency TADF white organic light-emitting devices（WOLED）was constructed by employing CDBP:PO-T2T exciplex as the host,2Cz PN and AnbTPA as blue and red dopants,respectively.By adjusting the carrier transport balance property and exciton distribution of each layer in EMLs,the WOLED with optimized device structure was obtained.As a result,the WOLED not only achieves high efficiency EL emission(maximum current efficiency,power efficiency,external quantum efficiency is 36.7 cdA-1,46.2 lmW-1,19.2%,respectively),and get high quality white light emission.At a luminance of 1000 cd m-2,the stable white emission exhibits a high color-rendering-index of 82,a CIE coordinate of（0.33,0.38）and a small CIE variation value of（0.00,0.02）in the luminance range of 100-3000 cdm-2.It is the best result of the current white OLEDs based on the TADF mechanism.2.The efficient red TADF exciplexes have been rarely reported,we propose a novel strategy to construct efficient red TADF exciplexes by introducing a phosphor as one component.Due to the strong spin-orbit coupling of heavy metal（e.g.,Ir,Pt,et al）ion cores,the NR decays will be evidently decreased for both singlet and triplet excitons,reducing these undesired excitons waste.Based on this strategy,we fabricate a red exciplex containing PO-T2T and Ir（ppy）3 as components and realize a red emission with a peak at 604 nm,a CIE coordinate of（0.55,0.44）,and a high maximum external quantum efficiency of 5%and operational time of 24 hour,aging at the same brightness of 1000 cdm-2.The high performance of red device is far superior than that of the device based on the conventional red exciplex emitter,proving the superiority of our novel strategy to construct red TADF exciplexes with phosphors.3.To address the low efficiency and serious roll-off at high excitation densities of TADF emitter based on organic light emitting devices,we propose a novel strategy for a new type of three-element exciplex TADF emitter by introducing a single-molecule TADF emitter and two tradition materials as one of the three-element exciplex compent.Such a new type of exciplex TADF emitter will have three RISC routes utilizing more triplet excitons,exhibit higher efficiency in the devices.Based on this strategy,we fabricated a high efficiency three-element exciplex CDBP:PO-T2T:DBT-spiro.The CDBP:PO-T2T:DBT-spiro exciplex based on OLEDs exhibits a low turn on voltage 2.4V and a high maximum EQE of 20.5%.Additionally,the EQE is still 14.2%at a high luminance of 1000 cdm-2,proving the superiority of our novel strategy.The outstanding performance is the best result of the current OLEDs based on the TADF exciplex.