Abstract

White polymer phosphorescent light-emitting diodes (WPLEDs) have been fabricated employing poly(ethylene glycol) dimethyl ether blended in the single active layer to enhance the emission efficiency. The devices have a simple sandwich architecture of ITO/poly((3,4-ethylenedioxythiophene): poly(styrenesulfonate)/emissive layer/CsF/Al. The emissive layer uses a blend of poly(9-vinylcarbazole), 1,3-bis[(4-tert- butylphenyl)-1,3,4-oxidiazolyl]phenylene, two or three phosphorescent dopants with complementary colors. The addition of poly(ethylene glycol) dimethyl ether enhances electron injection, transport, and the balance of densities of electrons and holes. The measured current efficiency in the front viewing direction is 17.5 cd/A at 1800 cdcm<sup>2</sup> for the two complementary WPLEDs, and 35.7 cd/A at 3000 cd/m<sup>2</sup> for the three complementary color WPLEDs. The current efficiencies remain high even at brightness levels up to 30,000 cd/m<sup>2</sup>. The high current efficiency is ascribed to the improved electron injection ability from the metal cathode, the enhanced charge carrier transport ability and the enhanced red emitting intensity by blending with PEG-DME. Also the low roll-off of the current efficiency was due to the lower triplet-polaron annihilation and the electric field-induced triplet exciton quenching by increased charge carrier transport in unipolar device and broadened recombination zone. The improved charge carrier injection at the interface and the enhanced charge carrier transport were resulted from specific interfacial interactions between PEG-DME and aluminum and higher electric field by blending with PEG-DME.

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2011 (4)

M. C. Gather, A. Köhnen, K. Meerholz, "White organic light-emitting diodes," Adv. Mater. 23, 233-248 (2011).

L. Xiao, Z. Chen, B. Qu, J. Luo, S. Kong, Q. Gong, J. Kido, "Recent progresses on materials for electrophosphorescent organic loght-emitting devices," Adv. Mater. 23, 926-952 (2011).

Z. Yu, M. Wang, G. Lei, J. Liu, L. Li, Q. Pei, "Stabilizing the dynamic p-i-n junction in polymer light-emitting electrochemical cells," J. Phys, Chem. Lett. 2, 367-372 (2011).

L. Li, J. Liu, Z. Yu, Q. Pei, "Highly efficient blue phosphorescent polymer light-emitting diodes by using interfacial modification," Appl. Phys. Lett. 98, (2011).

2010 (2)

M. Sun, C. Zhong, F. Li, Y. Cao, Q. Pei, "A fluorene-oxadiazole copolymer for white light-emitting electrochemical cells," Macromolecules 43, 1714-1718 (2010).

K. T. Kamtekar, A. P. Monkman, M. R. Bryce, "Recent advances in white organic light-emitting materials and devices (WOLEDs)," Adv. Mater. 22, 572-582 (2010).

2009 (7)

F. Huang, P. Shih, C. F. Shu, Y. Chi, A. K. Jen, "Highly efficient polymer white-light-emitting diodes based on lithium salts doped electron transporting layer," Adv. Mater. 21, 361-365 (2009).

G. Schwartz, S. Reineke, T. C. Rosenow, K. Walzer, K. Leo, "Triplet harvesting in hybrid white organic light-emitting diodes," Adv. Funct. Mater. 19, 1319-1333 (2009).

S. Reineke, F. Lindner, G. Schwartz, N. Seidler, K. Walzer, B. Lüssem, K. Leo, "White organic light-emitting diodes with fluorescent tube efficiency," Nature 459, 234-238 (2009).

F. Chen, S. Chien, Y. Chen, "Single-layer triplet white polymer light-emitting diodes incorporating polymer oxides: Effect of charge trapping at phosphorescent dopants," Appl. Phys. Lett. 94, (2009).

Z. Yu, M. Sun, Q. Pei, "Electrochemical formation of stable p-i-n junction in conjugated polymer thin films," J. Phys. Chem. B 113, 8481-8486 (2009).

L. Zeng, T. Y. Lee, P. Merkel, S. Chen, "A new class of non-conjugated bipolar hybrid hosts for phosphorescent organic light-emitting diodes," J. Mater. Chem. 19, 8772-8781 (2009).

F. Huang, Y. Zhang, M. S. Liu, A. Jen, "Electron-rich alcohol-soluble neutral conjugated polymers as highly efficient electron-injecting materials for polymer light-emitting diodes," Adv. Func. Mater. 19, 2457-2467 (2009).

2008 (3)

J. Wang, J. Yu, L. Li, T. Wang, K. Yuan, Y. Jiang, "Low roll-off power efficiency organic light-emitting diodes consisted of nondoped ultrathin phosphorescent layer," Appl. Phys. Lett. 92, (2008).

H. Wu, J. Zou, F. Liu, L. Wang, A. Mikhailovsky, G. C. Bazan, W. Yang, Y. Cao, "Efficient single active layer electrophosphorescent white polymer light-emitting diodes," Adv. Mater. 20, 696-702 (2008).

L. Li, J. Yu, X. Tang, T. Wang, W. Li, Y. Jiang, "Efficient bright white organic light-emitting diode based on non-doped ultrathin 5,6,11,12- tetraphenylnaphthacene layer," J. Luminesc. 128, 1783-1786 (2008).

2007 (4)

S. Reineke, K. Walzer, K. Leo, "Triplet-exciton quenching in organic phosphorescent light-emitting diodes with Ir-based emitters," Phys. Rev. B 75, (2007).

J. Wang, Y. D. Jiang, J. S. Yu, S. L. Lou, H. Lin, "Low operating voltage bright organic light-emitting diode using iridium complex doped in 4,4'-bis[N-1-napthyl-N-phenyl-amino]biphenyl," Appl. Phys. Lett. 91, (2007).

E. L. Williams, K. Haavisto, J. Li, G. E. Jabbour, "Excimer-based white phosphorescent organic light-emitting diodes with nearly 100% internal quantum efficiency," Adv. Mater. 19, 197-202 (2007).

M. Gather, R. Alle, H. Becker, K. Meerholz, "On the origin of the color shift in white-emitting OLEDs," Adv. Mater. 19, 4460-4465 (2007).

2006 (7)

J. X. Jiang, Y. H. Xu, W. Yang, R. Guan, Z. Q. Liu, H. Y. Zhen, Y. Cao, "High-efficiency white-light-emitting devices from a single polymer by mixing singlet and triplet emission," Adv. Mater. 18, 1769-1773 (2006).

J. Liu, Q. G. Zhou, Y. X. Cheng, Y. H. Geng, L. X. Wang, D. G. Ma, X. B. Jing, F. S. Wang, "White electroluminescence from a single-polymer system with simultaneous two-color emission: Polyfluorene as the blue host and a 2,1,3-benzothiadiazole derivative as the orange dopant," Adv. Funct. Mater. 16, 957-965 (2006).

H. J. Peng, X. L. Zhu, J. X. Sun, X. M. Yu, M. Wong, H. S. Kwok, "Efficiency improvement of phosphorescent organic light-emitting diodes using semitransparent Ag as anode," Appl. Phys. Lett. 88, (2006).

Y. Sun, N. C. Giebink, H. Kanno, B. Ma, M. E. Thompson, S. R. Forrest, "Management of singlet and triplet excitons for efficient white organic light-emitting devices," Nature 440, 908-912 (2006).

J. H. Jou, M. C. Sun, H. H. Chou, C. H. Li, "Efficient pure-white organic light-emitting diodes with a solution-processed, binary-host employing single emission layer," Appl. Phys. Lett. 88, (2006).

P. I. Shih, Y. H. Tseng, F. I. Wu, A. K. Dixit, C. F. Shu, "Stable and efficient white electroluminescent devices based on a single emitting layer of polymer blends," Adv. Funct. Mater. 16, 1582-1589 (2006).

Y. H. Xu, J. B. Peng, J. X. Jiang, W. Xu, W. Yang, Y. Cao, "Efficient white-light-emitting diodes based on polymer codoped with two phosphorescent dyes," Appl. Phys. Lett. 87, (2006).

2005 (2)

X. Gong, S. Wang, D. Moses, G. C. Bazan, A. J. Heeger, "Multilayer polymer light-emitting diodes: White-light emission with high efficiency," Adv. Mater. 17, 2053-2058 (2005).

Y. Niu, H. Ma, Q. Xu, A. Jen, "High-efficiency light-emitting diodes using neutral surfactants and aluminum cathode," Appl. Phys. Lett. 86, (2005).

2004 (7)

X. Gong, S. H. Lim, J. C. Ostrowski, D. Moses, C. J. Bardeen, G. C. Bazan, "Phosphorescence from iridium complexes doped into polymer blends," J. Appl. Phys. 95, 948-953 (2004).

X. Gong, W. Ma, J. C. Ostrowski, G. C. Bazan, D. Moses, A. J. Heeger, "White electrophosphorescent from semiconducting polymer blends," Adv. Mater. 16, 615-619 (2004).

Q. Xu, H. M. Duong, F. Wudl, Y. Yang, "Efficient single-layer twistacene-doped polymer white light-emitting diodes," Appl. Phys. Lett. 85, 3357-3359 (2004).

B. W. D'Andrade, S. R. Forrest, "White organic light-emitting devices for solid-state lighting," Adv. Mater. 16, 1585-1595 (2004).

B. W. D'Andrade, R. J. Holmes, S. R. Forrest, "Efficient organic electrophosphorescent white-light-emitting device with a triple doped emissive layer," Adv. Mater. 16, 624-628 (2004).

X. Y. Deng, W. M. Lau, K. Y. Wong, K. H. Low, H. F. Chow, Y. Cao, "High efficiency low operating voltage polymer light-emitting diodes with aluminum cathode," Appl. Phys. Lett. 84, 3522-3524 (2004).

C. Yang, C. Tai, I. Sun, "Synthesis of a high-efficiency red phosphorescent emitter for organic light-emitting diodes," J. Mater. Chem. 14, 947-950 (2004).

2003 (2)

R. J. Holmes, S. R. Forrest, Y.-J. Tung, R. C. Kwong, J. J. Brown, S. Garon, M. E. Thompson, "Blue organic electrophosphorescence using exothermic host–guest energy transfer," Appl. Phys. Lett. 82, 2422-2424 (2003).

B. Hu, F. E. Karasz, "Blue, green, red, and white electroluminescence from multichromophore polymer blends," J. Appl. Phys. 93, 1995-2001 (2003).

2002 (2)

J. Kalinowski, W. Stampor, J. Mezyk, M. Cocchi, D. Virgili, V. Fattori, P. Di Marco, "Quenching effects in organic electrophosphorescence," Phys. Rev. B 66, (2002).

B. W. D'Andrade, M. E. Thompson, S. R. Forrest, "Controlling exciton diffusion in multilayer white phosphorescent organic light emitting devices," Adv. Mater. 14, 147-151 (2002).

2001 (1)

P. A. Lane, L. C. Palilis, D. F. O'Brien, C. Giebeler, A. J. Cadby, D. G. Lidzey, A. J. Campbell, W. Blau, D. D. C. Bradley, "Origin of electrophosphorescence from a doped polymer light emitting diode," Phys. Rev. B 63, (2001).

2000 (2)

C. Adachi, M. A. Baldo, S. R. Forrest, "Electroluminescence mechanisms in organic light emitting devices employing a europium chelate doped in a wide energy gap bipolar conducting host," J. Appl. Phys. 87, 8049-8055 (2000).

M. A. Baldo, C. Adachi, S. R. Forrest, "Transient analysis of organic electrophosphorescence. II. Transient analysis of triplet-triplet annihilation," Phys. Rev. B 62, 10967-10977 (2000).

1995 (1)

J. Kido, M. Kimura, K. Nagai, "Multilayer white light-emitting organic electroluminescent device," Sci. 267, 1332-1334 (1995).

Adv. Func. Mater. (1)

F. Huang, Y. Zhang, M. S. Liu, A. Jen, "Electron-rich alcohol-soluble neutral conjugated polymers as highly efficient electron-injecting materials for polymer light-emitting diodes," Adv. Func. Mater. 19, 2457-2467 (2009).

Adv. Funct. Mater. (3)

P. I. Shih, Y. H. Tseng, F. I. Wu, A. K. Dixit, C. F. Shu, "Stable and efficient white electroluminescent devices based on a single emitting layer of polymer blends," Adv. Funct. Mater. 16, 1582-1589 (2006).

G. Schwartz, S. Reineke, T. C. Rosenow, K. Walzer, K. Leo, "Triplet harvesting in hybrid white organic light-emitting diodes," Adv. Funct. Mater. 19, 1319-1333 (2009).

J. Liu, Q. G. Zhou, Y. X. Cheng, Y. H. Geng, L. X. Wang, D. G. Ma, X. B. Jing, F. S. Wang, "White electroluminescence from a single-polymer system with simultaneous two-color emission: Polyfluorene as the blue host and a 2,1,3-benzothiadiazole derivative as the orange dopant," Adv. Funct. Mater. 16, 957-965 (2006).

Adv. Mater. (13)

E. L. Williams, K. Haavisto, J. Li, G. E. Jabbour, "Excimer-based white phosphorescent organic light-emitting diodes with nearly 100% internal quantum efficiency," Adv. Mater. 19, 197-202 (2007).

J. X. Jiang, Y. H. Xu, W. Yang, R. Guan, Z. Q. Liu, H. Y. Zhen, Y. Cao, "High-efficiency white-light-emitting devices from a single polymer by mixing singlet and triplet emission," Adv. Mater. 18, 1769-1773 (2006).

B. W. D'Andrade, R. J. Holmes, S. R. Forrest, "Efficient organic electrophosphorescent white-light-emitting device with a triple doped emissive layer," Adv. Mater. 16, 624-628 (2004).

H. Wu, J. Zou, F. Liu, L. Wang, A. Mikhailovsky, G. C. Bazan, W. Yang, Y. Cao, "Efficient single active layer electrophosphorescent white polymer light-emitting diodes," Adv. Mater. 20, 696-702 (2008).

F. Huang, P. Shih, C. F. Shu, Y. Chi, A. K. Jen, "Highly efficient polymer white-light-emitting diodes based on lithium salts doped electron transporting layer," Adv. Mater. 21, 361-365 (2009).

B. W. D'Andrade, M. E. Thompson, S. R. Forrest, "Controlling exciton diffusion in multilayer white phosphorescent organic light emitting devices," Adv. Mater. 14, 147-151 (2002).

X. Gong, W. Ma, J. C. Ostrowski, G. C. Bazan, D. Moses, A. J. Heeger, "White electrophosphorescent from semiconducting polymer blends," Adv. Mater. 16, 615-619 (2004).

X. Gong, S. Wang, D. Moses, G. C. Bazan, A. J. Heeger, "Multilayer polymer light-emitting diodes: White-light emission with high efficiency," Adv. Mater. 17, 2053-2058 (2005).

B. W. D'Andrade, S. R. Forrest, "White organic light-emitting devices for solid-state lighting," Adv. Mater. 16, 1585-1595 (2004).

K. T. Kamtekar, A. P. Monkman, M. R. Bryce, "Recent advances in white organic light-emitting materials and devices (WOLEDs)," Adv. Mater. 22, 572-582 (2010).

M. C. Gather, A. Köhnen, K. Meerholz, "White organic light-emitting diodes," Adv. Mater. 23, 233-248 (2011).

L. Xiao, Z. Chen, B. Qu, J. Luo, S. Kong, Q. Gong, J. Kido, "Recent progresses on materials for electrophosphorescent organic loght-emitting devices," Adv. Mater. 23, 926-952 (2011).

M. Gather, R. Alle, H. Becker, K. Meerholz, "On the origin of the color shift in white-emitting OLEDs," Adv. Mater. 19, 4460-4465 (2007).

Appl. Phys. Lett. (11)

L. Li, J. Liu, Z. Yu, Q. Pei, "Highly efficient blue phosphorescent polymer light-emitting diodes by using interfacial modification," Appl. Phys. Lett. 98, (2011).

Q. Xu, H. M. Duong, F. Wudl, Y. Yang, "Efficient single-layer twistacene-doped polymer white light-emitting diodes," Appl. Phys. Lett. 85, 3357-3359 (2004).

J. H. Jou, M. C. Sun, H. H. Chou, C. H. Li, "Efficient pure-white organic light-emitting diodes with a solution-processed, binary-host employing single emission layer," Appl. Phys. Lett. 88, (2006).

Y. H. Xu, J. B. Peng, J. X. Jiang, W. Xu, W. Yang, Y. Cao, "Efficient white-light-emitting diodes based on polymer codoped with two phosphorescent dyes," Appl. Phys. Lett. 87, (2006).

H. J. Peng, X. L. Zhu, J. X. Sun, X. M. Yu, M. Wong, H. S. Kwok, "Efficiency improvement of phosphorescent organic light-emitting diodes using semitransparent Ag as anode," Appl. Phys. Lett. 88, (2006).

F. Chen, S. Chien, Y. Chen, "Single-layer triplet white polymer light-emitting diodes incorporating polymer oxides: Effect of charge trapping at phosphorescent dopants," Appl. Phys. Lett. 94, (2009).

J. Wang, Y. D. Jiang, J. S. Yu, S. L. Lou, H. Lin, "Low operating voltage bright organic light-emitting diode using iridium complex doped in 4,4'-bis[N-1-napthyl-N-phenyl-amino]biphenyl," Appl. Phys. Lett. 91, (2007).

J. Wang, J. Yu, L. Li, T. Wang, K. Yuan, Y. Jiang, "Low roll-off power efficiency organic light-emitting diodes consisted of nondoped ultrathin phosphorescent layer," Appl. Phys. Lett. 92, (2008).

R. J. Holmes, S. R. Forrest, Y.-J. Tung, R. C. Kwong, J. J. Brown, S. Garon, M. E. Thompson, "Blue organic electrophosphorescence using exothermic host–guest energy transfer," Appl. Phys. Lett. 82, 2422-2424 (2003).

X. Y. Deng, W. M. Lau, K. Y. Wong, K. H. Low, H. F. Chow, Y. Cao, "High efficiency low operating voltage polymer light-emitting diodes with aluminum cathode," Appl. Phys. Lett. 84, 3522-3524 (2004).

Y. Niu, H. Ma, Q. Xu, A. Jen, "High-efficiency light-emitting diodes using neutral surfactants and aluminum cathode," Appl. Phys. Lett. 86, (2005).

J. Appl. Phys. (3)

X. Gong, S. H. Lim, J. C. Ostrowski, D. Moses, C. J. Bardeen, G. C. Bazan, "Phosphorescence from iridium complexes doped into polymer blends," J. Appl. Phys. 95, 948-953 (2004).

C. Adachi, M. A. Baldo, S. R. Forrest, "Electroluminescence mechanisms in organic light emitting devices employing a europium chelate doped in a wide energy gap bipolar conducting host," J. Appl. Phys. 87, 8049-8055 (2000).

B. Hu, F. E. Karasz, "Blue, green, red, and white electroluminescence from multichromophore polymer blends," J. Appl. Phys. 93, 1995-2001 (2003).

J. Luminesc. (1)

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