利用发光磁效应分析高温环境对OLED中激子演化的影响
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摘要
本文制备了基于红荧烯(Rubrene)材料的有机发光二极管(OLED),并利用磁电致发光效应(MEL)分析了高温环境对器件中激子演化的影响.器件的MEL在高、低外加磁场范围内的线型特征表明,室温下激子的演化以单重态激子分裂(STT)过程为主,而在420 K环境温度下,器件的STT过程减弱,但出现了系间窜越(ISC)这一激子演化过程.结合器件的表面形貌、发光-电流特性、电流效率和光谱,我们认为高温环境导致Rubrene薄膜中产生了大量的结构缺陷,限制了器件内部极化子对和激子的扩散,提高了单重态和三重态极化子对间的转换效率,从而导致高温环境下出现不利于内量子效率的ISC过程.但缺陷对激子的俘获作用会抑制单重态激子向三重态激子的转换,导致STT过程在高温环境下减弱,从而提升器件的内量子效率.本研究不仅有利于理解高温环境对Rubrene型OLED器件中激子演化过程的影响,还提供了一种利用有机发光磁效应无损探测器件发光层结构改变的技术方案.
An organic light-emitting diode(OLED) based on rubrene was fabricated, and the magneto-electroluminescence(MEL)was used to analyze the exciton evolutions in the device under high temperature environment. The MEL characteristics of the device in the high and low applied magnetic fields indicate that the exciton evolution at room temperature is dominated by singlet exciton splitting(STT) processes, 420 K ambient temperature the STT process weakens, but the exciton evolution process of intersystem crossing(ISC) occurs. Combined with the surface morphology, luminescencecurrent characteristics, current efficiency and spectrum of the device, we believe that the high temperature environment causes a large number of structure defect in the rubrene film. The defect limits the diffusion of the polaron pairs and excitons inside the device, and improves the conversion efficiency between the singlet polaron pairs and triplet polaron pairs, and results in an ISC process that is not conducive to internal quantum efficiency in high temperature. The capture of excitons inhibits the conversion of singlet excitons to triplet excitons, resulting in a weakening of the STT process in high temperature environments, thereby increasing the quantum efficiency of the device. It not only deepens the understanding of the influence of high temperature environment on the exciton evolution process in rubrene type OLED devices, but also provides a technical solution to monitor the structural changes of devices by using organic luminescence magnetic effect.
An organic light-emitting diode(OLED) based on rubrene was fabricated, and the magneto-electroluminescence(MEL)was used to analyze the exciton evolutions in the device under high temperature environment. The MEL characteristics of the device in the high and low applied magnetic fields indicate that the exciton evolution at room temperature is dominated by singlet exciton splitting(STT) processes, 420 K ambient temperature the STT process weakens, but the exciton evolution process of intersystem crossing(ISC) occurs. Combined with the surface morphology, luminescencecurrent characteristics, current efficiency and spectrum of the device, we believe that the high temperature environment causes a large number of structure defect in the rubrene film. The defect limits the diffusion of the polaron pairs and excitons inside the device, and improves the conversion efficiency between the singlet polaron pairs and triplet polaron pairs, and results in an ISC process that is not conducive to internal quantum efficiency in high temperature. The capture of excitons inhibits the conversion of singlet excitons to triplet excitons, resulting in a weakening of the STT process in high temperature environments, thereby increasing the quantum efficiency of the device. It not only deepens the understanding of the influence of high temperature environment on the exciton evolution process in rubrene type OLED devices, but also provides a technical solution to monitor the structural changes of devices by using organic luminescence magnetic effect.
引文
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2 Ma L,Zhang K,Kloc C,et al.Singlet fission in rubrene single crystal:Direct observation by femtosecond pump-probe spectroscopy.Phys Chem Chem Phys,2012,14:8307-8312
3詹义强.有机电致发光器件的稳定性研究.博士学位论文.上海:复旦大学,2005.3-7
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11 Xiang J,Chen Y,Yuan D,et al.Abnormal temperature dependent behaviors of intersystem crossing and triplet-triplet annihilation in organic planar heterojunction devices.Appl Phys Lett,2016,109:103301
12 Pan R H,Tang X T,Deng J Q,et al.Investigation of micro-mechanism in thermally activated delayed fluorescence quantum well devices by utilizing organic magnetic effects(in Chinese).Sci Sin-Tech,2018,48:745-754[潘睿亨,汤仙童,邓金秋,等.利用有机磁效应研究热活化延迟荧光量子阱器件中的微观机制.中国科学:技术科学,2018,48:745-754]
13 Chen Y B,Yuan D,Xiang J,et al.Analysis of triplet dissociation and electron scattering in the rubrene-based devices by utilizing magnetoconductance(in Chinese).Sci Sin-Tech,2016,46:61-67[陈颖冰,袁德,向杰,等.利用有机磁电导分析rubrene发光器件中三重态激子解离和电子散射过程.中国科学:技术科学,2016,46:61-67]
14 Jia W,Chen Q,Chen Y,et al.Magneto-conductance characteristics of trapped triplet-polaron and triplet-trapped polaron interactions in anthracene-based organic light emitting diodes.Phys Chem Chem Phys,2016,18:30733-30739
15 Chen L,Jia W,Lan Z,et al.Tuning the polarity of organic magnetic field effects in polymer light-emitting diodes by incorporating a colloidal quantum dots thin layer.Org Electron,2018,55:165-169
16 Zhang Y,Forrest S R.Triplets contribute to both an increase and loss in fluorescent yield in organic light emitting diodes.Phys Rev Lett,2012,108:267404
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19 Yoon Y,Kim S,Lee H,et al.Characterization of rubrene polycrystalline thin film transistors fabricated using various heat-treatment conditions.Thin Solid Films,2011,519:5562-5566
20 Wang F J,B?ssler H,Valy Vardeny Z.Magnetic field effects inπ-conjugated polymer-fullerene blends:Evidence for multiple components.Phys Rev Lett,2008,101:236805
21 Jia W,Chen Q,Chen L,et al.Molecular spacing modulated conversion of singlet fission to triplet fusion in rubrene-based organic light-emitting diodes at ambient temperature.J Phys Chem C,2016,120:8380-8386
22 Zhu H,Jia W,Chen L,et al.Trap-induced conversion from singlet fission to intersystem crossing via in situ heating of rubrene-based organic light-emitting diodes.J Mater Chem C,2019,7:553-557
23 Chen Y,Jia W,Xiang J,et al.Identify triplet-charge interaction in rubrene-based diodes using magneto-conductance:Coexistence of dissociation and scattering channels.Org Electron,2016,39:207-213
24 Dai Q,Bai S,Li H,et al.Template-free and non-hydrothermal synthesis of CeO2nanosheets via a facile aqueous-phase precipitation route with catalytic oxidation properties.CrystEngComm,2014,16:9817-9827
25 Bai J W,Lei Y L,Zhang Q M,et al.Control of singlet fission processes through modifying the molecular space of rubrene in OLEDs(in Chinese).Sci Sin-Phys Mech Astron,2013,43:1046-1051[白江文,雷衍连,张巧明,等.Rubrene分子间距对有机发光二极管中单重态激子裂变过程的调控.中国科学:物理学力学天文学,2013,43:1046-1051]
26 Jia W,Zhang Q,Chen L,et al.Spin-orbital coupling induced high-field decay of magneto-electroluminescence in pristine Alq3-based organic light-emitting diodes.Org Electron,2015,22:210-215
2 Ma L,Zhang K,Kloc C,et al.Singlet fission in rubrene single crystal:Direct observation by femtosecond pump-probe spectroscopy.Phys Chem Chem Phys,2012,14:8307-8312
3詹义强.有机电致发光器件的稳定性研究.博士学位论文.上海:复旦大学,2005.3-7
4 Deng J Q,Tang X T,Pan R H,et al.Abnormal magnetic field effects in doped organic light-emitting devices(in Chinese).Chin Sci Bull,2018,63:2974-2984[邓金秋,汤仙童,潘睿亨,等.有机发光掺杂器件中的反常磁效应.科学通报,2018,63:2974-2984]
5 Kalinowski J,Cocchi M,Virgili D,et al.Magnetic field effects on emission and current in Alq3-based electroluminescent diodes.Chem Phys Lett,2003,380:710-715
6 Tang X T,Xu J,Deng J Q,et al.Abnormal temperature dependent behaviors of intersystem crossing from rubrene guest dopant with Alq3and CBP hosts(in Chinese).Sci Sin-Phys Mech Astron,2018,48:117001[汤仙童,许静,邓金秋,等.红荧烯客体分子掺入Alq3和CBP主体的系间窜越的反常温度效应.中国科学:物理学力学天文学,2018,48:117001]
7 Podzorov V,Menard E,Borissov A,et al.Intrinsic charge transport on the surface of organic semiconductors.Phys Rev Lett,2004,93:086602
8 Hu Y Q,Liu D Y,Zang K K,et al.Investigation of electroluminescence mechanism in deep blue exciplex devices by utilizing magnetoelectroluminescence(in Chinese).Sci Sin-Tech,2017,47:373-382[胡叶倩,刘冬玉,臧克宽,等.利用有机发光磁效应研究深蓝色激基复合物的发光机理.中国科学:技术科学,2017,47:373-382]
9 Lei Y,Zhang Q,Chen L,et al.Ultralarge magneto-electroluminescence in exciplex-based devices driven by field-induced reverse intersystem crossing.Adv Opt Mater,2016,4:694-699
10 Tang X,Hu Y,Jia W,et al.Intersystem crossing and triplet fusion in singlet-fission-dominated rubrene-based OLEDs under high bias current.ACS Appl Mater Interfaces,2018,10:1948-1956
11 Xiang J,Chen Y,Yuan D,et al.Abnormal temperature dependent behaviors of intersystem crossing and triplet-triplet annihilation in organic planar heterojunction devices.Appl Phys Lett,2016,109:103301
12 Pan R H,Tang X T,Deng J Q,et al.Investigation of micro-mechanism in thermally activated delayed fluorescence quantum well devices by utilizing organic magnetic effects(in Chinese).Sci Sin-Tech,2018,48:745-754[潘睿亨,汤仙童,邓金秋,等.利用有机磁效应研究热活化延迟荧光量子阱器件中的微观机制.中国科学:技术科学,2018,48:745-754]
13 Chen Y B,Yuan D,Xiang J,et al.Analysis of triplet dissociation and electron scattering in the rubrene-based devices by utilizing magnetoconductance(in Chinese).Sci Sin-Tech,2016,46:61-67[陈颖冰,袁德,向杰,等.利用有机磁电导分析rubrene发光器件中三重态激子解离和电子散射过程.中国科学:技术科学,2016,46:61-67]
14 Jia W,Chen Q,Chen Y,et al.Magneto-conductance characteristics of trapped triplet-polaron and triplet-trapped polaron interactions in anthracene-based organic light emitting diodes.Phys Chem Chem Phys,2016,18:30733-30739
15 Chen L,Jia W,Lan Z,et al.Tuning the polarity of organic magnetic field effects in polymer light-emitting diodes by incorporating a colloidal quantum dots thin layer.Org Electron,2018,55:165-169
16 Zhang Y,Forrest S R.Triplets contribute to both an increase and loss in fluorescent yield in organic light emitting diodes.Phys Rev Lett,2012,108:267404
17 McEwan J A,Clulow A J,Nelson A,et al.Dependence of organic interlayer diffusion on glass-transition temperature in OLEDs.ACS Appl Mater Interf,2017,9:14153-14161
18 Tyagi P,Srivastava R,Giri L I,et al.Degradation of organic light emitting diode:Heat related issues and solutions.Synth Met,2016,216:40-50
19 Yoon Y,Kim S,Lee H,et al.Characterization of rubrene polycrystalline thin film transistors fabricated using various heat-treatment conditions.Thin Solid Films,2011,519:5562-5566
20 Wang F J,B?ssler H,Valy Vardeny Z.Magnetic field effects inπ-conjugated polymer-fullerene blends:Evidence for multiple components.Phys Rev Lett,2008,101:236805
21 Jia W,Chen Q,Chen L,et al.Molecular spacing modulated conversion of singlet fission to triplet fusion in rubrene-based organic light-emitting diodes at ambient temperature.J Phys Chem C,2016,120:8380-8386
22 Zhu H,Jia W,Chen L,et al.Trap-induced conversion from singlet fission to intersystem crossing via in situ heating of rubrene-based organic light-emitting diodes.J Mater Chem C,2019,7:553-557
23 Chen Y,Jia W,Xiang J,et al.Identify triplet-charge interaction in rubrene-based diodes using magneto-conductance:Coexistence of dissociation and scattering channels.Org Electron,2016,39:207-213
24 Dai Q,Bai S,Li H,et al.Template-free and non-hydrothermal synthesis of CeO2nanosheets via a facile aqueous-phase precipitation route with catalytic oxidation properties.CrystEngComm,2014,16:9817-9827
25 Bai J W,Lei Y L,Zhang Q M,et al.Control of singlet fission processes through modifying the molecular space of rubrene in OLEDs(in Chinese).Sci Sin-Phys Mech Astron,2013,43:1046-1051[白江文,雷衍连,张巧明,等.Rubrene分子间距对有机发光二极管中单重态激子裂变过程的调控.中国科学:物理学力学天文学,2013,43:1046-1051]
26 Jia W,Zhang Q,Chen L,et al.Spin-orbital coupling induced high-field decay of magneto-electroluminescence in pristine Alq3-based organic light-emitting diodes.Org Electron,2015,22:210-215
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