基于有机异质结C_(60)/ZnPc的绿色磷光TOLED
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摘要
以有机异质结C_(60)/ZnPc作为电荷产生层,制备结构为ITO/TPBi(40nm)/C_(60)(xnm)/ZnPc(x nm)/NPB(40nm)/Al(120nm)和ITO/TPBi(40nm)/LiF(ynm)/Al(2nm)/C_(60)(5nm)/ZnPc(5nm)/MoO_3(3nm)/NPB(40nm)/Al(120nm)的非发光倒置器件,其中x的值为0、5、10和15,y的值为0、0.5、1.0和1.5.实验证明,有机异质结C_(60)/ZnPc可在外电场下实现电荷分离,加入LiF/Al和MoO_3可更有效地提高电荷产生层的电荷分离和注入能力.基于LiF/Al/C_(60)/ZnPc/MoO_3结构,制备绿色磷光叠层有机发光二极管,进一步研究该电荷产生层对叠层器件的光电性能影响.结果表明,电荷产生层的电荷分离和注入可影响叠层器件内部的电荷注入平衡,进而对器件性能产生影响.当LiF、Al、C_(60)、ZnPc和MoO_3结构厚度分别为0.5nm、1nm、5nm、5nm和3nm时,电荷产生层产生的电荷与两侧电极注入的电荷达到匹配,使叠层器件具有最佳光电性能,获得了高效绿色磷光叠层器件,其驱动电压明显低于单层器件2倍,最大亮度、电流效率和功率效率分别达84 660cd·m~(-2)、94.7cd·A~(-1)和43lm·W~(-1).
Two inverted non-lighting devices with the configurations of ITO/TPBi(40 nm)/C_(60)(xnm)/ZnPc(xnm)/NPB(40 nm)/Al(120 nm)(x=0,5,10,and 15)and ITO/TPBi(40 nm)/LiF(ynm)/Al(2 nm)/C_(60)(5 nm)/ZnPc(5 nm)/MoO_3(3 nm)/NPB(40 nm)/Al(120 nm)(y=0,0.5,1.0,and 1.5)were fabricated.The experiments illustrate that the organic heterojunction of C_(60)/ZnPc can realize charge separation under external field and demonstrate that ability of charge separation and injection can be efficiently improved by the electron injection layer of LiF/Al and hole injection layer of MoO_3.C_(60)/ZnPcwas used as charge generation layer(CGL),LiF/Al and MoO_3 were employed as charge injection layers.Moreover,a series of green phosphorescent Tandem Organic Light-Emitting Diodes(TOLEDs)based on the multilayer structure of LiF/Al/C_(60)/ZnPc/MoO_3 was also fabricated to further explore the effect of the CGL on photoelectronic performances for tandem devices. Experimental results show that the performance of tandem devices can be influenced by the effect of charge separation and injection of CGL on charge-injection balance inside TOLEDs.When the multilayer structure is LiF(0.5 nm)/Al(1 nm)/C_(60)(5 nm)/ZnPc(5 nm)/MoO_3(3 nm),agreen TOLED with a better charge balance and an optimal device performance is achieved,the operating voltage of the tandem device is below two-fold of correspording single OLED.The peak luminance,peak current efficiency,and peak power efficiency for the green TOLED reach 84 660 cd·m-2,94.7 cd·A-1 and 43 lm·W-1,respectively,
Two inverted non-lighting devices with the configurations of ITO/TPBi(40 nm)/C_(60)(xnm)/ZnPc(xnm)/NPB(40 nm)/Al(120 nm)(x=0,5,10,and 15)and ITO/TPBi(40 nm)/LiF(ynm)/Al(2 nm)/C_(60)(5 nm)/ZnPc(5 nm)/MoO_3(3 nm)/NPB(40 nm)/Al(120 nm)(y=0,0.5,1.0,and 1.5)were fabricated.The experiments illustrate that the organic heterojunction of C_(60)/ZnPc can realize charge separation under external field and demonstrate that ability of charge separation and injection can be efficiently improved by the electron injection layer of LiF/Al and hole injection layer of MoO_3.C_(60)/ZnPcwas used as charge generation layer(CGL),LiF/Al and MoO_3 were employed as charge injection layers.Moreover,a series of green phosphorescent Tandem Organic Light-Emitting Diodes(TOLEDs)based on the multilayer structure of LiF/Al/C_(60)/ZnPc/MoO_3 was also fabricated to further explore the effect of the CGL on photoelectronic performances for tandem devices. Experimental results show that the performance of tandem devices can be influenced by the effect of charge separation and injection of CGL on charge-injection balance inside TOLEDs.When the multilayer structure is LiF(0.5 nm)/Al(1 nm)/C_(60)(5 nm)/ZnPc(5 nm)/MoO_3(3 nm),agreen TOLED with a better charge balance and an optimal device performance is achieved,the operating voltage of the tandem device is below two-fold of correspording single OLED.The peak luminance,peak current efficiency,and peak power efficiency for the green TOLED reach 84 660 cd·m-2,94.7 cd·A-1 and 43 lm·W-1,respectively,
引文
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[2]LIN Wen-yan,YU Ye,PENG Xue-kang,et al.Fabricating blue phosphorescent organic light-emitting devices by using B3PyPPM as electron transport layer[J].Acta Photonica Sinica,2018,47(12):1223001.林雯嫣,喻叶,彭雪康,等.以B3PyPPM为电子传输层制备蓝色磷光OLED器件[J].光子学报,2018,47(12):1223001.
[3]FUNG M K,LI Y Q,LIAO L S.Tandem organic light-emitting diodes[J].Advanced Materials,2016,28(47):10381-10408.
[4]MATSUMOTO T,NAKADA T,ENDO J,et al.Multiphoton organic EL device having charge generation layer[C].Oxford,UK:Blackwell Publishing Ltd,2003,34(1):979-981.
[5]YANG H,YU Y,WU L,et al.Highly efficient tandem organic light-emitting devices employing an easily fabricated charge generation unit[J].Applied Physics Express,2018,11(2):022101.
[6]KIM B S,CHAE H,CHUNG H K,et al.Electrical and optical analyses of tandem organic light-emitting diodes with organic charge-generation layer[J].AIP Advances,2018,8(6):065303.
[7]CHIBA T,PU Y J,KIDO J.Organic light-emitting devices with tandem structure[M].Springer,Cham,2017.
[8]HONG K,KIM K,KIM S,et al.Optical properties of WO3/Ag/WO3 multilayer as transparent electrode in top emitting OLEDs[C].Oxford,UK:Blackwell Publishing Ltd,2011,42(1):1784-1786.
[9]HFLE S,BRUNS M,STRSSLE S,et al.Tungsten oxide buffer layers fabricated in an Inert Sol-Gel process at room-temperature for blue organic light-emitting diodes[J].Advanced Materials,2013,25(30):4113-4116.
[10]LIU J,SHI X,WU X,et al.Inverted tandem phosphorescence organic light-emitting diodes based on MoO3/Al/Cs2CO3charge generation unit[J].Journal of Display Technology,2015,11(4):341-345.
[11]XIAO Z H,WU X M,HUA Y L,et al.Effect of NaCl doped into Bphen layer on the performance of tandem organic light-emitting diodes[J].Chinese Physics B,2014,23(8):087811.
[12]LIU Y,WU X,XIAO Z,et al.Highly efficient tandem OLED based on C60/rubrene:MoO3as charge generation layer and LiF/Al as electron injection layer[J].Applied Surface Science,2017,413(b):302-307.
[13]SUN H,CHEN Y,ZHU L,et al.Realization of optimal interconnector for tandem organic light-emitting diodes with record efficiency[J].Advanced Electronic Materials,2015,1(11):1500176.
[14]DAI Y,ZHANG H,ZHANG Z,et al.Highly efficient and stable tandem organic light-emitting devices based on HAT-CN/HAT-CN:TAPC/TAPC as a charge generation layer[J].Journal of Materials Chemistry C,2015,3(26):6809-6814.
[15]WANG Z,LIUF,CHEN A,et al.Buffer-modified C60/pentacene as organic charge generation layer based on Al and MoO3[J].Optoelectronics Letters,2018,14(4):286-290.
[16]GUO F,MA D.White organic light-emitting diodes based on tandem structures[J].Applied Physics Letters,2005,87(17):173510.
[17]CHAN M Y,LAI S L,LAU K M,et al.Influences of connecting unit architecture on the performance of tandem organic light-emitting devices[J].Advanced Functional Materials,2007,17(14):2509-2514.
[18]HAMWI S,MEYER J,KRGER M,et al.The role of transition metal oxides in charge generation layers for stacked organic light-emitting diodes[J].Advanced Functional Materials,2010,20(11):1762-1766.
[19]GUO Q,YANG D,CHEN J,et al.C70/C70:pentacene/pentacene organic heterojunction as the connecting layer for high performance tandem organic light-emitting diodes:Mechanism investigation of electron injection and transport[J].Journal of Applied Physics,2017,121(11):115502.
[20]ZHAO D,LIU H,MIAO Y,et al.A red tandem organic light-emitting diode based on organic photovoltaic-type charge generation layer[J].Organic Electronics,2016,32(5):1-6.
[21]HEO N,KIM Y,JUNG Y,et al.Interfacial electronic structure of C60/ZnPc/AZO on photoemission spectroscopy for organic photovoltaic applications[J].Chemical Physics,2016,478(10):145-149.
[22]LESSMANN R,HONG Z,SCHOLZ S,et al.Aging of flat heterojunction zinc phthalocyanine/fullerene C60organic solar cells[J].Organic Electronics,2010,11(4):539-543.
[23]JAVAID S,JAVED A M.An ab-initio density functional theory investigation of fullerene/Zn-phthalocyanine(C60/ZnPc)interface with face-on orientation[J].Journal of Applied Physics,2015,118(4):045305.
[24]KWONG C Y,DJURIIA B,CHUI P C,et al.Improvement of the efficiency of phthalocyanine organic Schottky solar cells with ITO electrode treatment[J].Applied Physics A,2003,77(3-4):555-560.
[25]CHEN Y,WANG Q,CHEN J,et al.Organic semiconductor heterojunction as charge generation layer in tandem organic light-emitting diodes for high power efficiency[J].Organic Electronics,2012,13(7):1121-1128.
[26]SHAHEEN S E,JABBOUR G E,MORRELL M M,et al.Bright blue organic light-emitting diode with improved color purity using a LiF/Al cathode[J].Journal of applied physics,1998,84(4):2324-2327.
[27]BROWN T M,FRIEND R H,MILLARD I S,et al.Electronic line-up in light-emitting diodes with alkali-halide/metal cathodes[J].Journal of applied physics,2003,93(10):6159-6172.
[28]LOU X,WANG X X,LIU C H,et al.Small-sized Al nanoparticles as electron injection hotspots in inverted organic light-emitting diodes[J].Organic Electronics,2016,28(1):88-93.