[1] Tang C W, VanSlyke S A. Organic electroluminescent diodes. Applied Physics Letters, 1987, 51(12): 913-915

[2] Fukase A, Dao K L T, Kido J. High-efficiency organic electroluminescent devices using iridium complex emitter and arylamine-containing polymer buffer layer. Ploymers for Advanced Technologies, 2002, 13(8): 601-604

[3] Tanaka D, Sasabe H, Li Y J, Su S J, Takeda T, Kido J. Ultra high efficiency green organic light-emitting devices. Japanese Journal of Applied Physics, 2007, 46(1): L10-L12

[4] Su S J, Tanaka D, Li Y J, Sasabe H, Takeda T, Kido J. Novel fourpyridylbenzene-armed biphenyls as electron-transport materials for phosphorescent OLEDs. Organic Letters, 2008, 10(5): 941-944

[5] Kim H, Cho N S, Oh H Y, Yang J H, Jeon W S, Park J S, Suh M C, Kwon J H. Highly efficient red phosphorescent dopants in organic light-emitting devices. Advanced Materials, 2011, 23(24): 2721-2726

[6] Fan C H, Sun P, Su T H, Cheng C H. Host and dopant materials for idealized deep-red organic electrophosphorescence devices. Advanced Materials, 2011, 23(26): 2981-2985

[7] Malliaras G G, Scott J C. The roles of injection and mobility in organic light emitting diodes. Journal of Applied Physics, 1998, 83(10): 5399-5403

[8] Polikarpov E, Swensen J S, Chopra N, So F, Padmaperuma A B. An ambipolar phosphine oxide-based host for high power efficiency blue phosphorescent organic light emitting devices. Applied Physics Letters, 2009, 94(22): 223304

[9] Gong S, Chen Y, Luo J, Yang C, Zhong C, Qin J, Ma D. Bipolar tetraarylsilanes as universal hosts for blue, green, orange, and white electrophosphorescence with high efficiency and low efficiency rolloff. Advanced Functional Materials, 2011, 21(6): 1168-1178

[10] Chou H H, Cheng C H. A highly efficient universal bipolar host for blue, green, and red phosphorescent OLEDs. Advanced Materials, 2010, 22(22): 2468-2471

[11] Xiao L, Su S J, Agata Y, Lan H, Kido J. Nearly 100% internal quantum efficiency in an organic blue-light electrophosphorescent device using a weak electron transporting material with a wide energy gap. Advanced Materials, 2009, 21(12): 1271-1274

[12] Lee J H, Huang C L, Hsiao C H, Leung M K, Yang C C, Chao C C. Blue phosphorescent organic light-emitting device with double emitting layer. Applied Physics Letters, 2009, 94(22): 223301

[13] Zhang X W, Li J, Khan M, Zhang L, Jiang X Y, Haq K, Zhu W Q, Zhang Z L. Improved chromaticity and electron injection in a blue organic light-emitting device by using a dual electron-transport layer with hole-blocking function. Semiconductor Science and Technology, 2009, 24(7): 075021

[14] Cai C, Su S J, Chiba T, Sasabe H, Pu Y J, Nakayama K, Kido J. Efficient low-driving-voltage blue phosphorescent homojunction organic light-emitting devices. Japanese Journal of Applied Physics, 2011, 50(4): 040204

[15] Tsuji H, Mitsui C, Sato Y, Nakamura E. Bis(carbazolyl)benzodifuran: a high-mobility ambipolar material for homojunction organic light-emitting diode devices. Advanced Materials, 2009, 21(37): 3776-3779

[16] Wang Q, Tao Y, Qiao X, Chen J, Ma D, Yang C, Qin J. Highperformance, phosphorescent, top-emitting organic light-emitting diodes with p-i-n homojunctions. Advanced Functional Materials, 2011, 21(9): 1681-1686

[17] Jang S E, Yook K S, Lee J Y. High power efficiency in simplified two layer blue phosphorescent organic light-emitting diodes. Organic Electronics, 2010, 11(6): 1154-1157

[18] Qiao X, Tao Y, Wang Q, Ma D, Yang C, Wang L, Qin J, Wang F. Controlling charge balance and exciton recombination by bipolar host in single-layer organic light-emitting diodes. Journal of Applied Physics, 2010, 108(3): 034508

[19] Zhang H, Huo C, Zhang J, Zhang P, Tian W, Wang Y. Efficient single-layer electroluminescent device based on a bipolar emitting boron-containing material. Chemical Communications (Cambridge), 2006, (3): 281-283

[20] Seo J H, Lee S J, Seo B M, Moon S J, Lee K H, Park J K, Yoon S S, Kim Y K. White organic light-emitting diodes showing nearly 100% internal quantum efficiency. Organic Electronics, 2010, 11(11): 1759-1766

[21] Chen H, Lee J, Shiau C. Electromagnetic modeling of organic lightemitting devices. Journal of Lightwave Technology, 2006, 24(6): 2450-2457

[22] Su S J, Chiba T, Takeda T, Kido J. Pyridine-containing triphenylbenzene derivatives with high electron mobility for highly efficient phosphorescent OLEDs. Advanced Materials, 2008, 20(11): 2125-2130