环境湿度对有机电致发光二极管功能材料的影响
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摘要
随着有机电致发光二极管(OLED)市场化进程加快,有机光电功能材料的应用日趋广泛,但环境湿度对OLED功能材料影响的研究鲜有报道。以典型的空穴传输材料N,N′-bis-(1-naphthyl)-N,N′-biphenyl-1,1′-biphenyl-4,4′-diamine(NPB)为例,将其分别置于环境湿度为5%,20%,35%和50%,环境温度均为25℃的条件下24h,以其为空穴传输层构建绿色荧光OLED器件;系统调查了NPB材料不同存储环境湿度对OLED器件性能的影响。结果表明,随着NPB存储环境湿度不断增加(5%~50%),器件性能逐渐降低,其中最大电流效率由3.96cd/A降低到3.31cd/A。进一步地,单载流子器件的电流-电压特性表明,随着环境湿度的增加,NPB空穴传输性能逐渐增强,这加剧了OLED器件中空穴和电子传输性能的不平衡,导致器件效率较低。此外,分析了NPB薄膜光致发光(PL)光谱随着材料存储湿度的增加逐渐红移的现象,这可能是由于水分子的侵入,使得NPB分子的局域激发态转换为具有强烈电荷转移特征的激发态的结果。
With accelerated marketization process of the organic light-emitting diode(OLED),organic optoelectric functional materials were more widely applied.However,the research results about the effect of environmental humidity on OLED functional materials were rarely reported.A typical hole-transporting material,N,N′-bis-(1-naphthyl)-N,N′-biphenyl-1,1′-biphenyl-4,4′-diamine(NPB)was taken as an example to investigate the humidity effect on the photoluminescent properties of organic materials and electroluminescent performance of and OLED devices.The NPB material was stored in various controlled relative humidity(RH)values at 5%,20%,35% and 50% at 25 ℃for 24 h.OLED devices were fabricated with the NPB as hole-transporting layers and tris(8-hydroxyquinoline)aluminium(Alq3)as light emitting layer.The effect of environmental humidity on the performance of OLED was studied.The results indicated that the performance of OLED was progressively decreased with increasing humidity ranging from 5%to 50%,and the maximum current efficiency reduced from3.96 to 3.31cd/A.Furthermore,current density-voltage characteristics of the hole-only devices presented that the hole mobility of NPB was increased with increasing humidity,which resulted in poor charge balance.The photoluminance spectra of the NPB film exhibited obvious red-shift with increasing the material storage humidity,which may due to the excited states from the locally excited state to an excited state with the strong charge transfer character.
With accelerated marketization process of the organic light-emitting diode(OLED),organic optoelectric functional materials were more widely applied.However,the research results about the effect of environmental humidity on OLED functional materials were rarely reported.A typical hole-transporting material,N,N′-bis-(1-naphthyl)-N,N′-biphenyl-1,1′-biphenyl-4,4′-diamine(NPB)was taken as an example to investigate the humidity effect on the photoluminescent properties of organic materials and electroluminescent performance of and OLED devices.The NPB material was stored in various controlled relative humidity(RH)values at 5%,20%,35% and 50% at 25 ℃for 24 h.OLED devices were fabricated with the NPB as hole-transporting layers and tris(8-hydroxyquinoline)aluminium(Alq3)as light emitting layer.The effect of environmental humidity on the performance of OLED was studied.The results indicated that the performance of OLED was progressively decreased with increasing humidity ranging from 5%to 50%,and the maximum current efficiency reduced from3.96 to 3.31cd/A.Furthermore,current density-voltage characteristics of the hole-only devices presented that the hole mobility of NPB was increased with increasing humidity,which resulted in poor charge balance.The photoluminance spectra of the NPB film exhibited obvious red-shift with increasing the material storage humidity,which may due to the excited states from the locally excited state to an excited state with the strong charge transfer character.
引文
[1]Tang C W,Vanslyke S A.Organic electroluminescent diodes[J].Applied Physics Letters,1987,51(12):913-915.
[2]Halls M D,Schlegel H B.Molecular orbital study of the first excited state of the OLED material tris(8-hydroxyquinoline)aluminum(Ⅲ)[J].Chemistry of Materials,2001,3(8):2632-2640.
[3]Park H,Lee J,Kang I,et al.Highly rigid and twisted anthracene derivatives:a strategy for deep blue OLED materials with theoretical limit efficiency[J].Journal of Materials Chemistry,2012,22(6):2695-2700.
[4]Wei B,Furukawa K,Amagai J,et al.A dynamic model for injection and transport of charge carriers in pulsed organic light-emitting diodes[J].Semiconductor Science&Technology,2004,19(5):L56-L59(4).
[5]Zhou L,Wanga A,Wu S,et al.All-organic active matrix flexible display[J].Applied Physics Letters,2006,88(8):083502(1-3).
[6]Geffroy B,Roy P,Prat C.Organic light-emitting diode(OLED)technology:materials,devices and display technologies[J].Polymer International,2006,55(6):572-582.
[7]Guo K,Li W,Zhang J,et al.Extremely high external quantum efficiency of inverted organic light-emitting diodes with low operation voltage and reduced efficiency roll-off by using sulfide-based double electron injection layers[J].RSC Advances,2016,6(60):55626-55634.
[8]Kamtekar K,Monkman A,Bryce M.Recent advances in white organic light-emitting materials and devices(WOLEDs)[J].Advanced Materials,2010,22(5):572-582.
[9]Liao Y,Yu F,Long L,et al.Low-cost and reliable thin film encapsulation for organic light emitting diodes using magnesium fluoride and zinc sulfide[J].Thin Solid Films,2011,519(7):2344-2348.
[10]Wei B,Liu J,Zhang Y,et al.Stable,glassy,and versatile binaphthalene derivatives capable of efficient hole transport,hosting,and deep-blue light emission[J].Advanced Functional Materials,2010,20(15):2448-2458.
[11]Yu J,Wei N,Li C,et al.Enhancement of efficiency and lifetime of blue organic light-emitting diodes using two dopants in single emitting layer[J].Advances in Materials Science&Engineering,2012,2012(5-6).
[12]Zhou T,Ngo T,Brown J,et al.Stable and efficient electrophosphorescent organic light-emitting devices grown by organic vapor phase deposition[J].Applied Physics Letters,2005,86(2):021107-021107-3.
[13]Adachi C,Baldo M,Thompson M,et al.Nearly 100%internal phosphorescence efficiency in an organic light-emitting device[J].Journal of Applied Physics,2001,90(10):5048-5051.
[14]Uoyama H,Goushi K,Shizu K,et al.Highly efficient organic light-emitting diodes from delayed fluorescence[J].Nature,2012,492(7428):234-238.
[15]Guo K,Chen C,Sun C,et al.Use of space interlayer in phosphorescent organic light-emitting diodes to improve efficiency and reduce efficiency roll-off[J].Journal of Physics D Applied Physics,2016,49(23):235105.
[16]Halls M,Tripp C,Schlegel H.Structure and infrared(IR)assignments for the OLED material:N,N′diphenyl-N,N′bis(1-naphthyl)-1,1′biphenyl-4,4′diamine(NPB)[J].Physical Chemistry Chemical Physics,2001,3(11):2131-2136.
[17]Li Z,Wu Z,Jiao B,et al.Novel 2,4-difluorophenylfunctionalized arylamine as hole-injecting/hole-transporting layers in organic light-emitting devices[J].Chemical Physics Letters,2012,527(8):36-41.
[18]Mu Qiang,Wang Xiufeng,Zhang Maili.Influence of hole transport layer NPB on performance of OLED[J].Materials Review,2009,23(2):15-16.牟强,王秀峰,张麦丽.空穴传输层NPB对OLED性能的影响[J].材料导报,2009,23(2):15-16.
[19]Mei Y,Wan M,Talib Z,et al.Optical properties for N,N′-bis(lnaphyhly)N,N′-diphenyl-1,1′-biphenyl-4,4′-diamine and tris(8-hydroxyquinolinato)aluminum in organic light emitting devices[J].Natural Science,2010,6(02):631-634.
[20]Huang Jin,Zhang Fanghui,Zhang Wei.New high-efficiency red phosphor OLED[J].Journal of Functional Materials,2013,44(17):2465-2467.黄晋,张方辉,张微.新型高效红色磷光OLED器件[J].功能材料,2013,44(17):2465-2467.
[21]Niu Jinghua,Peng Junbiao.Voltage controlled color tunable organic light-emitting diodes[J].Journal of Functional Materials,2010,41(1):12-13.牛晶华,彭俊彪.电压控制发光颜色的有机电致发光器件[J].功能材料,2010,41(1):12-13.
[22]Yu Y,Wu Z,Li Z,et al.Highly efficient deep-blue organic electroluminescent devices(CIEy≈0.08)doped with fluorinated 9,9′-bianthracene derivatives(fluorophores)[J].Journal of Materials Chemistry C,2013,48(1):8117-8127.
[23]Chen G,Sasabe H,Sasaki Y,et al.A series of squaraine dyes:effects of side chain and the number of hydroxyl groups on material properties and photovoltaic performance[J].Chemistry of Materials,2014,26(3):1356-1364.
[2]Halls M D,Schlegel H B.Molecular orbital study of the first excited state of the OLED material tris(8-hydroxyquinoline)aluminum(Ⅲ)[J].Chemistry of Materials,2001,3(8):2632-2640.
[3]Park H,Lee J,Kang I,et al.Highly rigid and twisted anthracene derivatives:a strategy for deep blue OLED materials with theoretical limit efficiency[J].Journal of Materials Chemistry,2012,22(6):2695-2700.
[4]Wei B,Furukawa K,Amagai J,et al.A dynamic model for injection and transport of charge carriers in pulsed organic light-emitting diodes[J].Semiconductor Science&Technology,2004,19(5):L56-L59(4).
[5]Zhou L,Wanga A,Wu S,et al.All-organic active matrix flexible display[J].Applied Physics Letters,2006,88(8):083502(1-3).
[6]Geffroy B,Roy P,Prat C.Organic light-emitting diode(OLED)technology:materials,devices and display technologies[J].Polymer International,2006,55(6):572-582.
[7]Guo K,Li W,Zhang J,et al.Extremely high external quantum efficiency of inverted organic light-emitting diodes with low operation voltage and reduced efficiency roll-off by using sulfide-based double electron injection layers[J].RSC Advances,2016,6(60):55626-55634.
[8]Kamtekar K,Monkman A,Bryce M.Recent advances in white organic light-emitting materials and devices(WOLEDs)[J].Advanced Materials,2010,22(5):572-582.
[9]Liao Y,Yu F,Long L,et al.Low-cost and reliable thin film encapsulation for organic light emitting diodes using magnesium fluoride and zinc sulfide[J].Thin Solid Films,2011,519(7):2344-2348.
[10]Wei B,Liu J,Zhang Y,et al.Stable,glassy,and versatile binaphthalene derivatives capable of efficient hole transport,hosting,and deep-blue light emission[J].Advanced Functional Materials,2010,20(15):2448-2458.
[11]Yu J,Wei N,Li C,et al.Enhancement of efficiency and lifetime of blue organic light-emitting diodes using two dopants in single emitting layer[J].Advances in Materials Science&Engineering,2012,2012(5-6).
[12]Zhou T,Ngo T,Brown J,et al.Stable and efficient electrophosphorescent organic light-emitting devices grown by organic vapor phase deposition[J].Applied Physics Letters,2005,86(2):021107-021107-3.
[13]Adachi C,Baldo M,Thompson M,et al.Nearly 100%internal phosphorescence efficiency in an organic light-emitting device[J].Journal of Applied Physics,2001,90(10):5048-5051.
[14]Uoyama H,Goushi K,Shizu K,et al.Highly efficient organic light-emitting diodes from delayed fluorescence[J].Nature,2012,492(7428):234-238.
[15]Guo K,Chen C,Sun C,et al.Use of space interlayer in phosphorescent organic light-emitting diodes to improve efficiency and reduce efficiency roll-off[J].Journal of Physics D Applied Physics,2016,49(23):235105.
[16]Halls M,Tripp C,Schlegel H.Structure and infrared(IR)assignments for the OLED material:N,N′diphenyl-N,N′bis(1-naphthyl)-1,1′biphenyl-4,4′diamine(NPB)[J].Physical Chemistry Chemical Physics,2001,3(11):2131-2136.
[17]Li Z,Wu Z,Jiao B,et al.Novel 2,4-difluorophenylfunctionalized arylamine as hole-injecting/hole-transporting layers in organic light-emitting devices[J].Chemical Physics Letters,2012,527(8):36-41.
[18]Mu Qiang,Wang Xiufeng,Zhang Maili.Influence of hole transport layer NPB on performance of OLED[J].Materials Review,2009,23(2):15-16.牟强,王秀峰,张麦丽.空穴传输层NPB对OLED性能的影响[J].材料导报,2009,23(2):15-16.
[19]Mei Y,Wan M,Talib Z,et al.Optical properties for N,N′-bis(lnaphyhly)N,N′-diphenyl-1,1′-biphenyl-4,4′-diamine and tris(8-hydroxyquinolinato)aluminum in organic light emitting devices[J].Natural Science,2010,6(02):631-634.
[20]Huang Jin,Zhang Fanghui,Zhang Wei.New high-efficiency red phosphor OLED[J].Journal of Functional Materials,2013,44(17):2465-2467.黄晋,张方辉,张微.新型高效红色磷光OLED器件[J].功能材料,2013,44(17):2465-2467.
[21]Niu Jinghua,Peng Junbiao.Voltage controlled color tunable organic light-emitting diodes[J].Journal of Functional Materials,2010,41(1):12-13.牛晶华,彭俊彪.电压控制发光颜色的有机电致发光器件[J].功能材料,2010,41(1):12-13.
[22]Yu Y,Wu Z,Li Z,et al.Highly efficient deep-blue organic electroluminescent devices(CIEy≈0.08)doped with fluorinated 9,9′-bianthracene derivatives(fluorophores)[J].Journal of Materials Chemistry C,2013,48(1):8117-8127.
[23]Chen G,Sasabe H,Sasaki Y,et al.A series of squaraine dyes:effects of side chain and the number of hydroxyl groups on material properties and photovoltaic performance[J].Chemistry of Materials,2014,26(3):1356-1364.