S. Barlow, Michael A. Fusella, Samik Jhulki, A. Kahn, N. Koch, E. Longhi, Kyung Min Lee, Xin Lin, S. Marder, K. Moudgil, Barry P Rand, C. Risko, Berthold Wegner, Fengyu Zhang
Electrical doping of organic semiconductors increases conductivity and reduces injection barriers from electrode materials, both of which effects can improve the performance of organic light-emitting diodes (OLEDs). However, the low electron affinities of typical OLED electron-transport materials make the identification of suitable n-dopants particularly challenging; electropositive metals such as the alkali metals are not easily handled and form monoatomic ions that are rather mobile in host materials, whereas molecular dopants that operate as simple one-electron reductants must have low ionization energies, which leads to severe air sensitivity. This presentation will discuss approaches to circumventing this issue by coupling electron transfer to other chemical reactivity. In particular, dimers formed by certain highly reducing organometallic sandwich compounds and organic radicals can be handled in air, yet have effective reducing potentials, corresponding to formation of the corresponding monomeric cations and contribution of two electrons to the semiconductor, of ca. –2.0 V vs. ferrocene. These values fall a little short of what is required for typical OLED materials; approaches to further extending the doping reach of these dimers will be described. One such approach involving photoirradiation of a dimer:semiconductor blend leads to metastable doping of a material with a redox potential of –2.24 V, which allows the fabrication of efficient OLEDs in which even high-workfunction electrodes, such as indium tin oxide, can be used as electron-injection contacts.
{"title":"Redox-active molecules as electrical dopants for OLED transport materials (Conference Presentation)","authors":"S. Barlow, Michael A. Fusella, Samik Jhulki, A. Kahn, N. Koch, E. Longhi, Kyung Min Lee, Xin Lin, S. Marder, K. Moudgil, Barry P Rand, C. Risko, Berthold Wegner, Fengyu Zhang","doi":"10.1117/12.2320651","DOIUrl":"https://doi.org/10.1117/12.2320651","url":null,"abstract":"Electrical doping of organic semiconductors increases conductivity and reduces injection barriers from electrode materials, both of which effects can improve the performance of organic light-emitting diodes (OLEDs). However, the low electron affinities of typical OLED electron-transport materials make the identification of suitable n-dopants particularly challenging; electropositive metals such as the alkali metals are not easily handled and form monoatomic ions that are rather mobile in host materials, whereas molecular dopants that operate as simple one-electron reductants must have low ionization energies, which leads to severe air sensitivity. This presentation will discuss approaches to circumventing this issue by coupling electron transfer to other chemical reactivity. In particular, dimers formed by certain highly reducing organometallic sandwich compounds and organic radicals can be handled in air, yet have effective reducing potentials, corresponding to formation of the corresponding monomeric cations and contribution of two electrons to the semiconductor, of ca. –2.0 V vs. ferrocene. These values fall a little short of what is required for typical OLED materials; approaches to further extending the doping reach of these dimers will be described. One such approach involving photoirradiation of a dimer:semiconductor blend leads to metastable doping of a material with a redox potential of –2.24 V, which allows the fabrication of efficient OLEDs in which even high-workfunction electrodes, such as indium tin oxide, can be used as electron-injection contacts.","PeriodicalId":158502,"journal":{"name":"Organic Light Emitting Materials and Devices XXII","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123770730","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Light emission in organic semiconductors is governed by the spin of excitons formed upon electrical excitation. Conventionally, 25% of excitons form as emissive singlets and 75% form non-emissive triplets. Exceeding this limit for OLEDs requires designing new materials. Developments in molecular design have allowed utilization of triplet excitons through either direct phosphorescence (1) or secondary processes converting a triplet into a singlet via a spin flip, creating “delayed” fluorescence. (2) Thermally Activated Delayed Fluorescence (TADF) has provided guidelines for creating donor-acceptor molecules, but the effects governing spin dynamics are still being explored. Increasingly, there is consensus that intersystem crossing,(ISC) cannot be understood from a static picture of the molecules; a more dynamic approach is necessary. Carbene Metal Amide (CMA) emitters (3) provide an excellent example, displaying large spectral shifts due to conformational reorganisation and highly variable intersystem crossing rates. In solid films, they have produced solution processed green OLEDs with record efficiencies. Here we show, starting from the green CMA archetypes, we can alter the molecular design to probe the effects of steric hindrance, spin-orbit coupling, and dipole strength on the emission properties. Using fast time resolved cryogenic PL spectroscopy we demonstrate the impact of changing the metal bridge atom on ISC, and explore high molecular weight variants for flexible electronics. We demonstrate these emitters can be tuned across the visible spectrum whilst retaining similar photophysical properties, and achieve efficient OLED devices via both solution and vacuum processing. We discuss their structure property relationships for emission, explore a new set of high efficiency OLED dopants, and provide fundamental insight into their spin conversion mechanism. From these studies we derive the first set of design rules for this new class of organometallic TADF emitters. 1) Very high-efficiency green organic light-emitting devices based on electrophosphorescence, Baldo et al. Appl. Phys. Lett. 1999 2) Highly efficient organic light-emitting diodes from delayed fluorescence. Uoyama et al. Nature 2012 3) High-performance light-emitting diodes based on carbene-metal-amides, Di et al. Science, 2017
{"title":"Exploring the photophysics of carbene metal amides (Conference Presentation)","authors":"Saul T. E. Jones, D. Credgington","doi":"10.1117/12.2322372","DOIUrl":"https://doi.org/10.1117/12.2322372","url":null,"abstract":"Light emission in organic semiconductors is governed by the spin of excitons formed upon electrical excitation. Conventionally, 25% of excitons form as emissive singlets and 75% form non-emissive triplets.\u0000\u0000Exceeding this limit for OLEDs requires designing new materials. Developments in molecular design have allowed utilization of triplet excitons through either direct phosphorescence (1) or secondary processes converting a triplet into a singlet via a spin flip, creating “delayed” fluorescence. (2)\u0000\u0000Thermally Activated Delayed Fluorescence (TADF) has provided guidelines for creating donor-acceptor molecules, but the effects governing spin dynamics are still being explored. Increasingly, there is consensus that intersystem crossing,(ISC) cannot be understood from a static picture of the molecules; a more dynamic approach is necessary. \u0000\u0000Carbene Metal Amide (CMA) emitters (3) provide an excellent example, displaying large spectral shifts due to conformational reorganisation and highly variable intersystem crossing rates. In solid films, they have produced solution processed green OLEDs with record efficiencies. \u0000\u0000Here we show, starting from the green CMA archetypes, we can alter the molecular design to probe the effects of steric hindrance, spin-orbit coupling, and dipole strength on the emission properties.\u0000\u0000Using fast time resolved cryogenic PL spectroscopy we demonstrate the impact of changing the metal bridge atom on ISC, and explore high molecular weight variants for flexible electronics. \u0000\u0000We demonstrate these emitters can be tuned across the visible spectrum whilst retaining similar photophysical properties, and achieve efficient OLED devices via both solution and vacuum processing. \u0000\u0000We discuss their structure property relationships for emission, explore a new set of high efficiency OLED dopants, and provide fundamental insight into their spin conversion mechanism. From these studies we derive the first set of design rules for this new class of organometallic TADF emitters. \u0000\u00001) Very high-efficiency green organic light-emitting devices based on electrophosphorescence, Baldo et al. Appl. Phys. Lett. 1999\u00002) Highly efficient organic light-emitting diodes from delayed fluorescence.\u0000 Uoyama et al. Nature 2012\u00003) High-performance light-emitting diodes based on carbene-metal-amides, Di et al. Science, 2017","PeriodicalId":158502,"journal":{"name":"Organic Light Emitting Materials and Devices XXII","volume":"48 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123771783","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The fundamental scientific challenge for organic light emitting diodes (OLEDs) is to successfully manage electronic spin. The excited state can only give out light if it can decay to the spin-0 ground state. Finding ways of harvesting light from spin-1 excitations has shaped OLED technology for the last three decades, since the choice of strategy to achieve this necessarily impacts materials design, device architecture, and the processes limiting device lifetime. Here we demonstrate a new approach to rapid triplet harvesting. We introduce a novel class of linear donor-bridge-acceptor light-emitting molecules which twist in their excited states, changing the coupling between electron and hole.(1) These enable doped polymer LEDs with near-100% internal quantum efficiency even at high brightness.(2) Our solution-processed OLEDs achieve current efficiency, power efficiency and brightness comparable to or exceeding those of state-of-the-art vacuum-deposited OLEDs and quantum dot LEDs. Using time-resolved spectroscopy, we establish that luminescence via triplets occurs on 100s of ns timescales at ambient temperature, after reverse intersystem crossing to singlets. We find this occurs because molecular geometries exist at which the singlet-triplet energy gap (exchange energy) is close to zero, such that rapid interconversion is possible. Unlike other low exchange energy systems, substantial oscillator strength is sustained at this point. We describe recent experimental and theoretical evidence for emission from these materials and show how it depends strongly in the interplay between rotational energetics, temperature, oscillator strength and the nanomorphology of the emissive layer. This gives us new tools to control emission colour and rate. Doing so, we tune emission from green to sky-blue, and achieve EQE at 1000 cdm-2 of nearly 30%. Based on this molecular motif, we realise new designs for molecular emitters realising sub-microsecond triplet emission and low roll-off in devices across the visible spectral range. 1. A. S. Romanov et al., Copper and Gold Cyclic (Alkyl)(amino)carbene Complexes with Sub-Microsecond Photoemissions: Structure and Substituent Effects on Redox and Luminescent Properties. Chem. - A Eur. J. 23, 4625–4637 (2017). 2. D. Di et al., High-performance light-emitting diodes based on carbene-metal-amides. Science. 356, 159–163 (2017).
有机发光二极管(oled)的基本科学挑战是成功地管理电子自旋。激发态只有衰变到自旋为0的基态才能发光。在过去的三十年里，寻找从自旋-1激发中收集光的方法塑造了OLED技术，因为实现这一目标的策略选择必然会影响材料设计、器件架构和限制器件寿命的工艺。在这里，我们展示了一种快速三联体收获的新方法。我们介绍了一种新型的线性给体-桥体-受体发光分子，它们在激发态中扭曲，改变电子和空穴之间的耦合。(1)这些使掺杂聚合物led即使在高亮度下也具有接近100%的内部量子效率。(2)我们的溶液处理oled的电流效率，功率效率和亮度可与最先进的真空沉积oled和量子点led相比较或超过。利用时间分辨光谱，我们确定在环境温度下，经过系统间反向交叉到单重态后，三重态发光发生在100ns的时间尺度上。我们发现这种情况的发生是因为分子的几何结构使得单线态和三重态的能隙(交换能)接近于零，使得快速的相互转换成为可能。与其他低交换能量系统不同，大量振荡器强度在这一点上得到维持。我们描述了这些材料发射的最新实验和理论证据，并展示了它如何强烈地依赖于旋转能量学、温度、振荡器强度和发射层纳米形貌之间的相互作用。这给了我们新的工具来控制发射颜色和速率。这样做，我们将排放从绿色调整为天蓝色，并在1000 cdm-2时达到近30%的EQE。基于这一分子基序，我们实现了在可见光谱范围内实现亚微秒三重态发射和低滚降的分子发射器的新设计。A. S. Romanov等，具有亚微秒光辐射的铜和金环(烷基)(氨基)碳配合物:结构和取代基对氧化还原和发光性能的影响。化学。——欧元。[j] .中国农业科学，2016,32(5):555 - 557。D. Di等人，基于碳金属酰胺的高性能发光二极管。科学通报，35(6)，39 - 43(2017)。
{"title":"Twistable charge-transfer states for next generation OLEDs (Conference Presentation)","authors":"D. Credgington","doi":"10.1117/12.2320541","DOIUrl":"https://doi.org/10.1117/12.2320541","url":null,"abstract":"The fundamental scientific challenge for organic light emitting diodes (OLEDs) is to successfully manage electronic spin. The excited state can only give out light if it can decay to the spin-0 ground state. Finding ways of harvesting light from spin-1 excitations has shaped OLED technology for the last three decades, since the choice of strategy to achieve this necessarily impacts materials design, device architecture, and the processes limiting device lifetime.\u0000\u0000Here we demonstrate a new approach to rapid triplet harvesting. We introduce a novel class of linear donor-bridge-acceptor light-emitting molecules which twist in their excited states, changing the coupling between electron and hole.(1) These enable doped polymer LEDs with near-100% internal quantum efficiency even at high brightness.(2) Our solution-processed OLEDs achieve current efficiency, power efficiency and brightness comparable to or exceeding those of state-of-the-art vacuum-deposited OLEDs and quantum dot LEDs. \u0000\u0000Using time-resolved spectroscopy, we establish that luminescence via triplets occurs on 100s of ns timescales at ambient temperature, after reverse intersystem crossing to singlets. We find this occurs because molecular geometries exist at which the singlet-triplet energy gap (exchange energy) is close to zero, such that rapid interconversion is possible. Unlike other low exchange energy systems, substantial oscillator strength is sustained at this point.\u0000\u0000We describe recent experimental and theoretical evidence for emission from these materials and show how it depends strongly in the interplay between rotational energetics, temperature, oscillator strength and the nanomorphology of the emissive layer. This gives us new tools to control emission colour and rate. Doing so, we tune emission from green to sky-blue, and achieve EQE at 1000 cdm-2 of nearly 30%. Based on this molecular motif, we realise new designs for molecular emitters realising sub-microsecond triplet emission and low roll-off in devices across the visible spectral range.\u0000\u00001. A. S. Romanov et al., Copper and Gold Cyclic (Alkyl)(amino)carbene Complexes with Sub-Microsecond Photoemissions: Structure and Substituent Effects on Redox and Luminescent Properties. Chem. - A Eur. J. 23, 4625–4637 (2017).\u00002. D. Di et al., High-performance light-emitting diodes based on carbene-metal-amides. Science. 356, 159–163 (2017).","PeriodicalId":158502,"journal":{"name":"Organic Light Emitting Materials and Devices XXII","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132522123","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Organic Light Emitting Diodes, OLEDs, are now a common feature in mobile phones and ultrathin televisions. Light generation by electroluminescence in the best OLEDs can have 100% internal charge to photon conversion efficiency. This requires very efficient triplet to singlet excited state harvesting, and has been the strict preserve of electrophosphorescence heavy metal complex emitters until now. However, recently it has been discovered that all organic, donor-acceptor (DA) charge transfer molecules can also yield such efficient triplet harvesting and OLEDS with 100% internal efficiency can be fabricated. Here the process of triplet harvesting is by thermally activated delayed fluorescence, ‘TADF’, i.e. E-type delayed fluorescence, and in this talk I shall elucidate how this triplet harvesting mechanism works, including the mechanism that allows very efficient reverse intersystem crossing in a non heavy metal containing molecule, second order vibronic coupling spin orbit coupling. 1, 2 Detailed photophysical measurements of intramolecular charge transfer (ICT) states in the solid state will be used to guide our interpretation. Temperature dependent time resolved emission, delayed emission and photoinduced absorption are used to map the energy levels involved in molecule decay, and through detailed quantum chemical modelling, electron exchange energies and other energy barriers of the systems are determined with the various excited states involved in the reversed intersystem crossing mechanism elucidated. From these measurements rates of rISC can be obtained. This will be explained. One concern over TADF has been the potential trade off between rISC rate and PLAY because of the orthogonality of the mechanisms controlling these two key photophysical processes. From a new design of TADF molecule, we will demonstrate that it is indeed possible to achieve both high PLQY (100%) and a rISC rate > 107 s-1, seemingly impossible from the original description of rISC and TADF. This gives a new design criterion for TADF emitters. Our vibronic coupling second order spin orbit mechanism has been used to explain the observed photophysical phenomena and from further quantum chemical helps to explain how this paradox can be overcome. With very fast risk and high PLQY comes low efficiency roll-off at high brightness. References 1. Etherington, M. K., Gibson, J., Higginbotham, H. F., Penfold, T. J. & Monkman, A. P. Revealing the spin-vibronic coupling mechanism of thermally activated delayed fluorescence. Nat Commun 7, 13680 (2016). 2. Gibson, J., Monkman, A. P. & Penfold, T. J. The Importance of Vibronic Coupling for Efficient Reverse Intersystem Crossing in Thermally Activated Delayed Fluorescence Molecules. ChemPhysChem 1–7 (2016). doi:10.1002/cphc.201600662 3. Dias, F. B. et al. The Role of Local Triplet Excited States in Thermally-Activated Delayed Fluorescence: Photophysics and Devices. Adv. Sci. 3, 1600080 (2016). 4. M.K. Etherington, F. Franchello, J.
有机发光二极管(OLEDs)现在是手机和超薄电视的常见特征。在最好的oled中，电致发光产生的光可以具有100%的内电荷到光子的转换效率。这需要非常有效的三重态到单线态激发态的收获，并且到目前为止一直是电磷光重金属络合物发射体的严格保护。然而，最近发现，所有有机的供体-受体(DA)电荷转移分子也可以产生这种高效的三重态收获，并且可以制造出具有100%内部效率的oled。在这里，三重态收集的过程是通过热激活延迟荧光，' TADF '，即e型延迟荧光，在这次演讲中，我将阐明三重态收集机制是如何工作的，包括在非重金属分子中允许非常有效的反向系统间交叉的机制，二阶振动耦合自旋轨道耦合。1,2固体中分子内电荷转移(ICT)状态的详细光物理测量将用于指导我们的解释。利用温度依赖的时间分辨发射、延迟发射和光诱导吸收来绘制分子衰变所涉及的能级，并通过详细的量子化学建模，确定了系统的电子交换能和其他能垒，阐明了系统间交叉机制所涉及的各种激发态。从这些测量可以得到rISC的速率。这将被解释。由于控制这两个关键光物理过程的机制的正交性，对TADF的一个关注是rISC速率和PLAY之间的潜在权衡。从一种新的TADF分子设计中，我们将证明它确实有可能同时实现高PLQY(100%)和rISC速率bb0 107 s-1，这从rISC和TADF的原始描述中似乎是不可能的。这为TADF发射架的设计提供了新的准则。我们的振动耦合二阶自旋轨道机制已被用来解释观测到的光物理现象，并从量子化学进一步解释如何克服这一悖论。伴随着非常快的风险和高PLQY，高亮度下的低效率滚转。References1。Etherington, M. K, Gibson, J.， Higginbotham, H. F, Penfold, T. J. & Monkman, A. P.揭示热激活延迟荧光的自旋振动耦合机制。生物医学工程学报，2016,32(5):391 - 391。Gibson, J, Monkman, A. P. & Penfold, T. J.热激活延迟荧光分子中振动耦合对有效反向系统间交叉的重要性。化学物理学报1-7(2016)。doi: 10.1002 / cphc.2016006623。迪亚斯，f.b.等。局部三重态激发态在热激活延迟荧光中的作用:光物理和器件。科学进展3,1600080(2016). 3。M.K. Etherington, F. Franchello, J. Gibson, T. Northey, J. Santos, J. s . Ward, H.F. Higginbotham, P. Data, A. Kurowska, P.L. Dos Santos, D.R. Graves, A.S. Batsanov, F.B. Dias, M.R. Bryce, T.J. Penfold, A.P. Monkman，高效热激活延迟荧光发射器设计的区域和构象异构化关键，自然科学学报，8,14987(2017)。
{"title":"Towards ultra-high efficiency low roll off TADF OLEDs (Conference Presentation)","authors":"A. Monkman","doi":"10.1117/12.2322615","DOIUrl":"https://doi.org/10.1117/12.2322615","url":null,"abstract":"Organic Light Emitting Diodes, OLEDs, are now a common feature in mobile phones and ultrathin televisions. Light generation by electroluminescence in the best OLEDs can have 100% internal charge to photon conversion efficiency. This requires very efficient triplet to singlet excited state harvesting, and has been the strict preserve of electrophosphorescence heavy metal complex emitters until now. However, recently it has been discovered that all organic, donor-acceptor (DA) charge transfer molecules can also yield such efficient triplet harvesting and OLEDS with 100% internal efficiency can be fabricated. Here the process of triplet harvesting is by thermally activated delayed fluorescence, ‘TADF’, i.e. E-type delayed fluorescence, and in this talk I shall elucidate how this triplet harvesting mechanism works, including the mechanism that allows very efficient reverse intersystem crossing in a non heavy metal containing molecule, second order vibronic coupling spin orbit coupling. 1, 2\u0000\u0000Detailed photophysical measurements of intramolecular charge transfer (ICT) states in the solid state will be used to guide our interpretation. Temperature dependent time resolved emission, delayed emission and photoinduced absorption are used to map the energy levels involved in molecule decay, and through detailed quantum chemical modelling, electron exchange energies and other energy barriers of the systems are determined with the various excited states involved in the reversed intersystem crossing mechanism elucidated. From these measurements rates of rISC can be obtained. This will be explained.\u0000\u0000One concern over TADF has been the potential trade off between rISC rate and PLAY because of the orthogonality of the mechanisms controlling these two key photophysical processes. From a new design of TADF molecule, we will demonstrate that it is indeed possible to achieve both high PLQY (100%) and a rISC rate > 107 s-1, seemingly impossible from the original description of rISC and TADF. This gives a new design criterion for TADF emitters.\u0000\u0000Our vibronic coupling second order spin orbit mechanism has been used to explain the observed photophysical phenomena and from further quantum chemical helps to explain how this paradox can be overcome. With very fast risk and high PLQY comes low efficiency roll-off at high brightness. \u0000\u0000References\u00001. Etherington, M. K., Gibson, J., Higginbotham, H. F., Penfold, T. J. & Monkman, A. P. Revealing the spin-vibronic coupling mechanism of thermally activated delayed fluorescence. Nat Commun 7, 13680 (2016).\u00002. Gibson, J., Monkman, A. P. & Penfold, T. J. The Importance of Vibronic Coupling for Efficient Reverse Intersystem Crossing in Thermally Activated Delayed Fluorescence Molecules. ChemPhysChem 1–7 (2016). doi:10.1002/cphc.201600662\u00003. Dias, F. B. et al. The Role of Local Triplet Excited States in Thermally-Activated Delayed Fluorescence: Photophysics and Devices. Adv. Sci. 3, 1600080 (2016).\u00004. M.K. Etherington, F. Franchello, J.","PeriodicalId":158502,"journal":{"name":"Organic Light Emitting Materials and Devices XXII","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132530640","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Exciplexes formed by intermolecular charge transfer between electron-donating and electron-accepting molecules have attracted much attention because of their triplet harvesting characteristics for highly efficient OLEDs. Similar to thermally activated delayed fluorescence (TADF), exciplex exhibit an extremely small singlet-triplet energy splitting, and allow upconversion from triplet states to singlet states. Here, we will show our recent results on high performance OLEDs based on exciplex hosts and emitters. Phosphorescent white OLEDs with simple structure were successfully fabricated by doping a blue emitter in the exciplex host and then inserting an ultrathin nondoped orange layer within the blue emissive zone. By optimizing the location of the orange emitter, a high power efficiency of 75.3 lm/W was achieved in the phosphorescent white OLED with reduced efficiency roll-off. Hybrid white OLEDs were fabricated by using exciplex as both of the blue fluorescent emitter and the host for phosphorescent emitters. An exciplex-sandwich emissive architecture was designed to precisely manipulate the exciton allocation. And a high external quantum efficiency of 28.3% and a high power efficiency of 102.9 lm/W were realized in the hybrid white OLEDs, which remain as high as 25.8% and 63.5 lm/W at 1000 cd/m2. Most recently, we proposed a method by exciplex engineering to fabricate fluorescent OLEDs with high efficiency and low efficiency roll-off, which could open a useful avenue to design all-fluorescent white OLEDs without TADF emitters for high performance lighting.
{"title":"Fully utilizing exciton for high performance organic light emitting diodes based on exciplex hosts and emitters (Conference Presentation)","authors":"Dongge Ma","doi":"10.1117/12.2323868","DOIUrl":"https://doi.org/10.1117/12.2323868","url":null,"abstract":"Exciplexes formed by intermolecular charge transfer between electron-donating and electron-accepting molecules have attracted much attention because of their triplet harvesting characteristics for highly efficient OLEDs. Similar to thermally activated delayed fluorescence (TADF), exciplex exhibit an extremely small singlet-triplet energy splitting, and allow upconversion from triplet states to singlet states. Here, we will show our recent results on high performance OLEDs based on exciplex hosts and emitters. \u0000Phosphorescent white OLEDs with simple structure were successfully fabricated by doping a blue emitter in the exciplex host and then inserting an ultrathin nondoped orange layer within the blue emissive zone. By optimizing the location of the orange emitter, a high power efficiency of 75.3 lm/W was achieved in the phosphorescent white OLED with reduced efficiency roll-off.\u0000Hybrid white OLEDs were fabricated by using exciplex as both of the blue fluorescent emitter and the host for phosphorescent emitters. An exciplex-sandwich emissive architecture was designed to precisely manipulate the exciton allocation. And a high external quantum efficiency of 28.3% and a high power efficiency of 102.9 lm/W were realized in the hybrid white OLEDs, which remain as high as 25.8% and 63.5 lm/W at 1000 cd/m2. \u0000Most recently, we proposed a method by exciplex engineering to fabricate fluorescent OLEDs with high efficiency and low efficiency roll-off, which could open a useful avenue to design all-fluorescent white OLEDs without TADF emitters for high performance lighting.","PeriodicalId":158502,"journal":{"name":"Organic Light Emitting Materials and Devices XXII","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132639070","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The mobile display market is strongly shifting towards AMOLED technology which enables curved and flexible displays. Therefore, the demand for highly efficient OLED emitters to reduce power consumption and increase display resolution at the same time is growing. There are efficient green and red OLED emitters in mass production already, but there is no efficient blue counterpart. CYNORA´s approach to provide efficient blue OLED emitters is based on thermally activated delayed fluorescence technology. TADF emitter systems allow for an efficiency increase of up to four times compared to conventional fluorescent systems by utilizing both triplet and singlet excitons for the emission of light. At the same time, they maintain deep blue emission, i.e. CIEy < 0.2. Herein, we review our recent progress on TADF emitters, reaching 20% EQE at 1000 nits in deep blue OLED devices (< 460 nm peak wavelength) together with reasonable LT97 values. The performance of these new blue TADF emitters is now in the range of commercial requirements for blue emitters in OLED displays.
{"title":"Highly efficient deep blue TADF emitter materials for OLED displays (Conference Presentation)","authors":"Matthias Budzynski, T. Baumann, D. Ambrosek","doi":"10.1117/12.2322127","DOIUrl":"https://doi.org/10.1117/12.2322127","url":null,"abstract":"The mobile display market is strongly shifting towards AMOLED technology which enables curved and \u0000flexible displays. Therefore, the demand for highly efficient OLED emitters to reduce power \u0000consumption and increase display resolution at the same time is growing. There are efficient green and \u0000red OLED emitters in mass production already, but there is no efficient blue counterpart. \u0000CYNORA´s approach to provide efficient blue OLED emitters is based on thermally activated delayed \u0000fluorescence technology. TADF emitter systems allow for an efficiency increase of up to four times \u0000compared to conventional fluorescent systems by utilizing both triplet and singlet excitons for the \u0000emission of light. At the same time, they maintain deep blue emission, i.e. CIEy < 0.2. \u0000Herein, we review our recent progress on TADF emitters, reaching 20% EQE at 1000 nits in deep blue \u0000OLED devices (< 460 nm peak wavelength) together with reasonable LT97 values. The performance of \u0000these new blue TADF emitters is now in the range of commercial requirements for blue emitters in \u0000OLED displays.","PeriodicalId":158502,"journal":{"name":"Organic Light Emitting Materials and Devices XXII","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131643694","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Current OLED displays rely on a circularly polarised (CP) filter to enhance contrast by trapping ambient light inside the display. However, this means that 50% of the randomly polarised light emitted from each OLED pixel never leaves the screen, halving display efficiency and operational lifetime. One simple route to fabricate CP-emitting OLEDs is to use electroluminescent (EL) polymer – small molecule blends. Our approach is to pair a chiral small molecule with a non-chiral device optimised polymer, which allows for CP-dependent applications while retaining much of the performance properties of the original polymer. Previously circularly polarised polymer emission has been achieved via thick cholesteric stacks of liquid crystalline polymers, where linearly polarised light becomes circularly polarised. Here we show that it is possible to control whether cholesteric packing or chiral dipole dominates emission using film thickness; remarkably this allows us to change the handedness of the CP EL emission in the same materials system. We compare how the chemical structure of the non-chiral polymer and post-deposition processing impacts the chiroptical response of the resulting device, in an effort to provide a set of design rules for future high performance CP-OLEDs. We demonstrate a liquid-crystalline light emitting polymer with a record high induced absorption dissymmetry factor, which additionally shows no change in device characteristics (no trapping, etc) in the blends, as well as strong CP-PL and EL emission.
{"title":"Strong induced chiroptical effects in light emitting polymer blends (Conference Presentation)","authors":"Jessica Wade, A. Campbell, Li Wan, M. Fuchter","doi":"10.1117/12.2321171","DOIUrl":"https://doi.org/10.1117/12.2321171","url":null,"abstract":"Current OLED displays rely on a circularly polarised (CP) filter to enhance contrast by trapping ambient light inside the display. However, this means that 50% of the randomly polarised light emitted from each OLED pixel never leaves the screen, halving display efficiency and operational lifetime. One simple route to fabricate CP-emitting OLEDs is to use electroluminescent (EL) polymer – small molecule blends. Our approach is to pair a chiral small molecule with a non-chiral device optimised polymer, which allows for CP-dependent applications while retaining much of the performance properties of the original polymer. Previously circularly polarised polymer emission has been achieved via thick cholesteric stacks of liquid crystalline polymers, where linearly polarised light becomes circularly polarised. Here we show that it is possible to control whether cholesteric packing or chiral dipole dominates emission using film thickness; remarkably this allows us to change the handedness of the CP EL emission in the same materials system. We compare how the chemical structure of the non-chiral polymer and post-deposition processing impacts the chiroptical response of the resulting device, in an effort to provide a set of design rules for future high performance CP-OLEDs. We demonstrate a liquid-crystalline light emitting polymer with a record high induced absorption dissymmetry factor, which additionally shows no change in device characteristics (no trapping, etc) in the blends, as well as strong CP-PL and EL emission.","PeriodicalId":158502,"journal":{"name":"Organic Light Emitting Materials and Devices XXII","volume":"112 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128542955","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Romanov, D. Di, Le Yang, P. Conaghan, Saul T. E. Jones, R. Friend, Mikko Linnolahti, D. Credgington, M. Bochmann
Current materials leaders in OLED technology are largely based on phosphorescent iridium complexes and Thermally Activated Delayed Fluorescence (TADF) materials which emit by harvesting light from all excited states ensuring nearly 100% internal quantum efficiency (IQE). Although, high efficiency red, green and blue OLEDs were realized, very short operating stability remains a fundamental challenge for blue OLEDs. Here we present our materials design strategy. We have recently designed numerous linear coinage metal complexes with efficient photo- and electroluminescent properties.[1,2] Our materials are composed of the donor and acceptor ligands which are linked by a coinage metal atom. Linear geometry of coinage metal complexes enables rotational flexibility. Rotation about the metal-ligand bond allowed us to tune the energy gap between singlet and triplet excited states. When the gap is close to zero, facile intersystem crossing and reversed intersystem crossing are possible which enables efficient singlet and triplet excited state harvesting. Depending on the value of the energy gap we have designed various functional materials with phosphorescent or delayed fluorescence properties. As a proof of concept, we fabricated OLED devices with exceptionally high external quantum efficiencies (>28% EQE) in both solution-processed and vacuum-deposited OLEDs.[3] Power and current efficiency are comparable to or exceeding state-of-the-art phosphorescent OLEDs and quantum dot LEDs. Our materials possess short excited state lifetime (100-300 ns) for the delayed emission which is highly important for the fabrication of the long-lived OLEDs. [1] A.S. Romanov, D. Di, L. Yang, J. Fernandez-Cestau, C.R. Becker, C.E. James, B. Zhu, M. Linnolahti, D. Credgington, M. Bochmann, Chem. Commun., 52, 6379 (2016) [2] A.S. Romanov, C.R. Becker, C.E. James, D. Di, D. Credgington, M. Linnolahti, M. Bochmann, Chem. Eur. J., 23, 4625 (2017). [3] D. Di, A.S. Romanov, L. Yang, J.M. Richter, J.P.H. Rivett, S. Jones, T.H. Thomas, M.A. Jalebi, R.H. Friend, M. Linnolahti, M. Bochmann, D. Credgington, Science, 356, 159 (2017)
目前OLED技术的领军材料主要基于磷光铱配合物和热激活延迟荧光(TADF)材料，这些材料通过收集所有激发态的光来发射，确保近100%的内部量子效率(IQE)。虽然已经实现了高效率的红、绿、蓝oled，但对于蓝oled来说，非常短的工作稳定性仍然是一个根本性的挑战。在这里，我们提出了我们的材料设计策略。我们最近设计了许多具有高效光致发光和电致发光特性的线性铸币金属配合物。[1,2]我们的材料是由一个金属原子连接的给体和受体配体组成的。铸币金属配合物的线性几何结构使其具有旋转灵活性。围绕金属配体键的旋转使我们能够调整单线态和三重态激发态之间的能隙。当间隙接近于零时，系统间可以轻松穿越和反向穿越，从而实现有效的单重态和三重态激发态收获。根据能隙的大小，我们设计了各种具有磷光或延迟荧光特性的功能材料。作为概念验证，我们在溶液处理和真空沉积的OLED中制造了具有极高外部量子效率(>28% EQE)的OLED器件功率和电流效率与最先进的磷光oled和量子点led相当或超过。我们的材料具有较短的延迟发射激发态寿命(100-300 ns)，这对制造长寿命oled非常重要A.S. Romanov, D. Di, L. Yang, J. Fernandez-Cestau, C.R. Becker, C.E. James, B. Zhu, M. Linnolahti, D. Credgington, M. Bochmann, Chem。Commun。[10]刘建军，刘建军，刘建军，刘建军，刘建军，等。欧元。[J] .中国生物医学工程学报，2017,46 (5):444 - 444D. Di, A.S. Romanov, L. Yang, J.M. Richter, J.P.H. Rivett, S. Jones, T.H. Thomas, M.A. Jalebi, R.H. Friend, M. Linnolahti, M. Bochmann, D. Credgington, Science, 356, 159 (2017)
{"title":"Linear carbene metal amides as a new class of emitters for highly efficient solution-processed and vapor-deposited OLEDs (Conference Presentation)","authors":"A. Romanov, D. Di, Le Yang, P. Conaghan, Saul T. E. Jones, R. Friend, Mikko Linnolahti, D. Credgington, M. Bochmann","doi":"10.1117/12.2320824","DOIUrl":"https://doi.org/10.1117/12.2320824","url":null,"abstract":"Current materials leaders in OLED technology are largely based on phosphorescent iridium complexes and Thermally Activated Delayed Fluorescence (TADF) materials which emit by harvesting light from all excited states ensuring nearly 100% internal quantum efficiency (IQE). Although, high efficiency red, green and blue OLEDs were realized, very short operating stability remains a fundamental challenge for blue OLEDs. Here we present our materials design strategy.\u0000We have recently designed numerous linear coinage metal complexes with efficient photo- and electroluminescent properties.[1,2] Our materials are composed of the donor and acceptor ligands which are linked by a coinage metal atom. Linear geometry of coinage metal complexes enables rotational flexibility. Rotation about the metal-ligand bond allowed us to tune the energy gap between singlet and triplet excited states. When the gap is close to zero, facile intersystem crossing and reversed intersystem crossing are possible which enables efficient singlet and triplet excited state harvesting. Depending on the value of the energy gap we have designed various functional materials with phosphorescent or delayed fluorescence properties. As a proof of concept, we fabricated OLED devices with exceptionally high external quantum efficiencies (>28% EQE) in both solution-processed and vacuum-deposited OLEDs.[3] Power and current efficiency are comparable to or exceeding state-of-the-art phosphorescent OLEDs and quantum dot LEDs. Our materials possess short excited state lifetime (100-300 ns) for the delayed emission which is highly important for the fabrication of the long-lived OLEDs.\u0000[1] A.S. Romanov, D. Di, L. Yang, J. Fernandez-Cestau, C.R. Becker, C.E. James, B. Zhu, M. Linnolahti, D. Credgington, M. Bochmann, Chem. Commun., 52, 6379 (2016)\u0000[2] A.S. Romanov, C.R. Becker, C.E. James, D. Di, D. Credgington, M. Linnolahti, M. Bochmann, Chem. Eur. J., 23, 4625 (2017).\u0000[3] D. Di, A.S. Romanov, L. Yang, J.M. Richter, J.P.H. Rivett, S. Jones, T.H. Thomas, M.A. Jalebi, R.H. Friend, M. Linnolahti, M. Bochmann, D. Credgington, Science, 356, 159 (2017)","PeriodicalId":158502,"journal":{"name":"Organic Light Emitting Materials and Devices XXII","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114851993","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Excited charge transfer complexes (Exciplex) formed between donor and acceptor materials are frequently encountered in organic photonic devices such as in organic light emitting diodes and organic photovoltaics. Formation of exciplexes can be easily identified by the observation of the red shifted emission from those of the component molecules. Generally the PL efficiency of the exciplexes is low so that OLEDs are designed not to form exciplexes at the organic/organic junctions. Formation of exciplexes at the D/A junction is also to be avoided in OPVs since it reduces the dissociation probability of geminate electron-hole pairs formed at the interface. In this presentation we will firstly discuss on the nature of exciplex including the electronic structure, emission processes and diffusion. Further discussion will be given to the application of exciplex forming systems as the triplet harvesting fluorescent molecular system and as the co-host for phosphorescent and fluorescent dopants for ultimate efficiency in OLEDs.
{"title":"Excited complex: Its nature and applications (Conference Presentation)","authors":"Jang‐Joo Kim, Chang‐Ki Moon, Hwang-Bum Kim","doi":"10.1117/12.2322802","DOIUrl":"https://doi.org/10.1117/12.2322802","url":null,"abstract":"Excited charge transfer complexes (Exciplex) formed between donor and acceptor materials are frequently encountered in organic photonic devices such as in organic light emitting diodes and organic photovoltaics. Formation of exciplexes can be easily identified by the observation of the red shifted emission from those of the component molecules. Generally the PL efficiency of the exciplexes is low so that OLEDs are designed not to form exciplexes at the organic/organic junctions. Formation of exciplexes at the D/A junction is also to be avoided in OPVs since it reduces the dissociation probability of geminate electron-hole pairs formed at the interface. In this presentation we will firstly discuss on the nature of exciplex including the electronic structure, emission processes and diffusion. Further discussion will be given to the application of exciplex forming systems as the triplet harvesting fluorescent molecular system and as the co-host for phosphorescent and fluorescent dopants for ultimate efficiency in OLEDs.","PeriodicalId":158502,"journal":{"name":"Organic Light Emitting Materials and Devices XXII","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130466612","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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