红荧烯发光器件中电流与温度调控的微观演化过程
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摘要
有机发光磁效应对有机半导体中激发态的微观过程有指纹式响应,本文采用这一灵敏方法探究了红荧烯(Rubrene)发光器件中微观机制随电流与温度的演化.实验结果表明:室温下,注入较小电流(5~100μA)时,Rubrene中主要发生单重态激子的分裂(singlet fission,SF),且该过程几乎不受电流变化的影响;注入中等电流(100~1000μA)时,除发生SF外,由直接注入的三重态激子还可以发生聚合反应(triplet fusion,TF);注入大电流(1000~4500μA)时,除了SF和TF,还出现了系间窜越过程(inter-system crossing,ISC).从室温到20 K的降温过程中,SF变弱,TF增强,ISC过程也越来越强.本器件中ISC随电流与温度的演化规律均与常规发光器件中的规律相反.我们采用相关微观过程的率常数以及不同电流和温度下激发态的寿命对实验结果进行了较好解释,这对深入理解Rubrene在有机发光中的微观机制有一定的促进作用.
The magnetic field effects(MFEs) of organic light-emitting diodes(OLEDs) is usually used as a fingerprint response for the microscopic mechanism of excited states in organic semiconductor. In this work, this sensitive method is employed to investigate the evolution of microscopic mechanism with the currents and temperatures in rubrene-based OLEDs. The experimental results of room temperature show that singlet fission(SF), which is rarely dependent on the bias currents, is the primary process in the device at small injection currents; at moderate injection currents, triplet fusion(SF) process gradually occurs besides the SF process; at large injection currents,the inter-system crossing(ISC) process appears except the process of TF and SF. When the temperature is reduced from ambient temperature down to 20 K, the intensity of SF process decreases, but both TF and ISC process become stronger. The temperature and current dependences of ISC in this rubrene-based OLEDs is contrary to those reported from conventional devices without SF process.We combine the rate constants of micro processes with the current-and temperature-dependent lifetime of excited states to well explain the experimental results. Our work is beneficial to a profound understanding of the microscopic mechanisms for OLEDs.
The magnetic field effects(MFEs) of organic light-emitting diodes(OLEDs) is usually used as a fingerprint response for the microscopic mechanism of excited states in organic semiconductor. In this work, this sensitive method is employed to investigate the evolution of microscopic mechanism with the currents and temperatures in rubrene-based OLEDs. The experimental results of room temperature show that singlet fission(SF), which is rarely dependent on the bias currents, is the primary process in the device at small injection currents; at moderate injection currents, triplet fusion(SF) process gradually occurs besides the SF process; at large injection currents,the inter-system crossing(ISC) process appears except the process of TF and SF. When the temperature is reduced from ambient temperature down to 20 K, the intensity of SF process decreases, but both TF and ISC process become stronger. The temperature and current dependences of ISC in this rubrene-based OLEDs is contrary to those reported from conventional devices without SF process.We combine the rate constants of micro processes with the current-and temperature-dependent lifetime of excited states to well explain the experimental results. Our work is beneficial to a profound understanding of the microscopic mechanisms for OLEDs.
引文
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10 Kuwae H,Nitta A,Yoshida K,et al.Suppression of external quantum efficiency roll-off of nanopatterned organic-light emitting diodes at high current densities.J Appl Phys,2015,118:155501
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13 Jia W Y,Chen Q S,Chen L X,et al.Molecular spacing modulated conversion of singlet fission to triplet fusion in rubrene-based organic lightemitting diodes at ambient temperature.J Phys Chem C,2016,120:8380-8386
14 Greyson E C,Stepp B R,Chen X D,et al.Singlet exciton fission for solar cell applications:Energy aspects of interchromophore coupling.J Phys Chem B,2010,114:14223-14232
15 Zhang Y F,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
16 Reusswig P D,Congreve D N,Thompson N J,et al.Enhanced external quantum efficiency in an organic photovoltaic cell via singlet fission exciton sensitizer.Appl Phys Lett,2012,101:113304
17 Chen D C,Wang Z H,Wang D,et al.Efficient exciplex organic light-emitting diodes with a bipolar acceptor.Org Electron,2015,25:79-84
18 Smith M B,Michl J.Singlet fission.Chem Rev,2010,110:6891-6936
19 Desai P,Shakya P,Kreouzis T,et al.Magnetoresistance and efficiency measurements of Alq3-based OLEDs.Phys Rev B,2007,75:094423
20 Hu B,Wu Y.Tuning magnetoresistance between positive and negative values in organic semiconductors.Nat Mater,2007,6:985-991
21 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
22 Lei Y L,Zhang Y,Liu R,et al.Driving current and temperature dependent magnetic-field modulated electroluminescence in Alq3-based organic light emitting diode.Org Electron,2009,10:889-894
23 Wen X M,Yu P,Yuan C T,et al.Singlet and triplet carrier dynamics in rubrene single crystal.J Phys Chem C,2013,117:17741-17747
24 Liu H,Jia W Y,Zhang Y,et al.Tuning magneto-electroluminescence in organic light emitting diodes by controlling the competition between singlet fission and triplet fusion.Synth Met,2014,198:6-9
25陈中海,李婧,熊祖洪,等.Rubrene掺杂有机薄膜中的单重态激子裂变过程.科学通报,2014,59:1942-1948
26 Wagemans W,Koopmans B.Spin transport and magnetoresistance in organic semiconductors.Phys Status Solidi B,2011,248:1029-1041
27 Li J,Chen Z H,Zhang Q M,et al.Temperature-dependent singlet exciton fission observed in amorphous rubrene films.Org Electron,2015,26:213-217
28 Tarasov V V,Zoriniants G E,Shushin A I,et al.The role of spin-lattice relaxation in magnetic field effects on the luminescence of amorphous and polycrystalline rubrene films.Chem Phys Lett,1997,267:58-64
29张勇,刘荣,雷衍连,等.基于Alq3的有机发光二极管中的瞬时荧光与延迟荧光.中国科学:物理学力学天文学,2010,40:416-424
2 Yamagishi M,Takeya J,Tominari Y,et al.High-mobility double-gate organic single-crystal transistors with organic crystal gate insulators.Appl Phys Lett,2007,90:182117
3陈秋松,袁德,贾伟尧,等.利用磁致发光曲线研究Rubrene器件中激子分裂和湮没过程.物理学报,2015,64:177801
4 Karak S,Lim J A,Ferdous S,et al.Photovoltaic effect at the Schottky interface with organic single crystal rubrene.Adv Funct Mater,2014,24:1039-1046
5 Piland G B,Burdett J J,Kurunthu D,et al.Magnetic field effects on singlet fission and fluorescence decay dynamics in amorphous rubrene.J Phys Chem C,2013,117:1224-1236
6 Burdett J J,Bardeen C J.The dynamics of singlet fission in crystalline tetracene and covalent analogs.Acc Chem Res,2013,46:1312-1320
7 Setoguchi Y,Adachi C.Suppression of roll-off characteristics of electroluminescence at high current densities in organic light emitting diodes by introducing reduced carrier injection barriers.J Appl Phys,2010,108:064516
8 Zhao Y K,Yun F,Huang Y,et al.Efficiency roll-off suppression in organic light-emitting diodes using size-tunable bimetallic bowtie nanoantennas at high current densities.Appl Phys Lett,2016,109:013303
9 Zang F X,Sum T C,Huan A C H,et al.Reduced efficiency roll-off in phosphorescent organic light emitting diodes at ultrahigh current densities by suppression of triplet-polaron quenching.Appl Phys Lett,2008,93:023309
10 Kuwae H,Nitta A,Yoshida K,et al.Suppression of external quantum efficiency roll-off of nanopatterned organic-light emitting diodes at high current densities.J Appl Phys,2015,118:155501
11 Bai J W,Chen P,Lei Y L,et al.Studying singlet fission and triplet fusion by magneto-electroluminescence method in singlet-triplet energyresonant organic light-emitting diodes.Org Electron,2014,15:169-174
12卢晨蕾,贾伟尧,白江文,等.有机发光二极管中多种微观机制共存的有机磁效应.中国科学:技术科学,2015,45:396-402
13 Jia W Y,Chen Q S,Chen L X,et al.Molecular spacing modulated conversion of singlet fission to triplet fusion in rubrene-based organic lightemitting diodes at ambient temperature.J Phys Chem C,2016,120:8380-8386
14 Greyson E C,Stepp B R,Chen X D,et al.Singlet exciton fission for solar cell applications:Energy aspects of interchromophore coupling.J Phys Chem B,2010,114:14223-14232
15 Zhang Y F,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
16 Reusswig P D,Congreve D N,Thompson N J,et al.Enhanced external quantum efficiency in an organic photovoltaic cell via singlet fission exciton sensitizer.Appl Phys Lett,2012,101:113304
17 Chen D C,Wang Z H,Wang D,et al.Efficient exciplex organic light-emitting diodes with a bipolar acceptor.Org Electron,2015,25:79-84
18 Smith M B,Michl J.Singlet fission.Chem Rev,2010,110:6891-6936
19 Desai P,Shakya P,Kreouzis T,et al.Magnetoresistance and efficiency measurements of Alq3-based OLEDs.Phys Rev B,2007,75:094423
20 Hu B,Wu Y.Tuning magnetoresistance between positive and negative values in organic semiconductors.Nat Mater,2007,6:985-991
21 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
22 Lei Y L,Zhang Y,Liu R,et al.Driving current and temperature dependent magnetic-field modulated electroluminescence in Alq3-based organic light emitting diode.Org Electron,2009,10:889-894
23 Wen X M,Yu P,Yuan C T,et al.Singlet and triplet carrier dynamics in rubrene single crystal.J Phys Chem C,2013,117:17741-17747
24 Liu H,Jia W Y,Zhang Y,et al.Tuning magneto-electroluminescence in organic light emitting diodes by controlling the competition between singlet fission and triplet fusion.Synth Met,2014,198:6-9
25陈中海,李婧,熊祖洪,等.Rubrene掺杂有机薄膜中的单重态激子裂变过程.科学通报,2014,59:1942-1948
26 Wagemans W,Koopmans B.Spin transport and magnetoresistance in organic semiconductors.Phys Status Solidi B,2011,248:1029-1041
27 Li J,Chen Z H,Zhang Q M,et al.Temperature-dependent singlet exciton fission observed in amorphous rubrene films.Org Electron,2015,26:213-217
28 Tarasov V V,Zoriniants G E,Shushin A I,et al.The role of spin-lattice relaxation in magnetic field effects on the luminescence of amorphous and polycrystalline rubrene films.Chem Phys Lett,1997,267:58-64
29张勇,刘荣,雷衍连,等.基于Alq3的有机发光二极管中的瞬时荧光与延迟荧光.中国科学:物理学力学天文学,2010,40:416-424