9 Kido J, Matsumoto T, Nakada T, et al. High efficiency organic EL devices having charge generation layers. SID Int Symp Dig Tech, 2003,34: 964-965？？
[2]
11 Kanno H, Holmes R J, Sun Y, et al. White stacked electrophosphorescent organic light-emitting devices employing MoO3 as a chargegenerationlayer. Adv Mater, 2006, 18: 339-342？？
[3]
12 Guo F W, Ma D G. White organic light-emitting diodes based on tandem structures. Appl Phys Lett, 2005, 87: 173510？？
[4]
13 Matsumoto T, Nakada T, Endo J, et al. Multiphoton organic EL device having charge generation layer. SID Int Symp Dig Tech, 2003, 34:979-981？？
[5]
16 Liao L S, Klubek K P, Tang C W. High-efficiency tandem organic light-emitting diodes. Appl Phys Lett, 2004, 84: 167-169？？
[6]
18 Lai S L, Chan M Y, Fung M K, et al. Copper hexadecafluorophthalocyanine and copper phthalocyanine as a pure organic connecting unitin blue tandem organic light-emitting devices. J Appl Phys, 2007, 101: 014509？？
[7]
20 Kanno H, Hamada Y, Nishimura K, et al. High efficiency stacked organic light-emitting diodes employing Li2O as a connecting layer. JpnJ Appl Phys 1, 2006, 45: 9219-9223？？
[8]
23 Liao L S, Ren X, Begley W J, et al. Tandem white OLEDs combining fluorescent and phosphorescent emission. SID Int Symp Dig Tech,2008, 39: 818-821？？
[9]
31 Verlaak S, Beljonne D, Cheyns D, et al. Electronic structure and geminate pair energetics at organic-organic interfaces: The case ofpentacene/C60 heterojunctions. Adv Funct Mater, 2009, 19: 3809-3814？？
[10]
32 Bao Q Y, Yang J P, Li Y Q, et al. Electronic structures of MoO3-based charge generation layer for tandem organic light-emitting diodes.Appl Phys Lett, 2010, 97: 063303？？
[11]
33 Ishii H, Sugiyama K, Ito E, et al. Energy level alignment and interfacial electronic structures at organic metal and organic organicinterfaces. Adv Mater, 1999, 11: 605-625？？
[12]
1 Tang C W, Vanslyke S A. Organic electroluminescent diodes. Appl Phys Lett, 1987, 51: 913-915？？
[13]
3 Forrest S R, Burrows P E, Shen Z, et al. The stacked OLED (SOLED): A new type of organic device for achieving high-resolutionfull-color displays. Synthetic Met, 1997, 91: 9-13？？
[14]
4 Kido J, Kimura M, Nagai K. Multilayer white light-emitting organic electroluminescent device. Science, 1995, 267: 1332-1334？？
[15]
7 Gather M C, Kohnen A, Meerholz K. White organic light-emitting diodes. Adv Mater, 2011, 23: 233-248？？
[16]
8 VanSlyke S A, Chen C H, Tang C W. Organic electroluminescent devices with improved stability. Appl Phys Lett, 1996, 69: 2160-2162？？
[17]
2 Burroughes J H, Bradley D D C, Brown A R, et al. Light-emitting-diodes based on conjugated polymers. Nature, 1990, 347: 539-541？？
[18]
5 Baldo M A, O'Brien D F, You Y, et al. Highly efficient phosphorescent emission from organic electroluminescent devices. Nature, 1998,395: 151-154？？
[19]
6 Xiao L X, Chen Z J, Qu B, et al. Recent progresses on materials for electrophosphorescent organic light-emitting devices. Adv Mater,2011, 23: 926-952？？
[20]
10 Chang C C, Hwang S W, Chen C H, et al. High-efficiency organic electroluminescent device with multiple emitting units. Jpn J Appl Phys1, 2004, 43: 6418-6422？？
[21]
14 Liao L S, Slusarek W K, Hatwar T K, et al. Tandem organic light-emitting mode using hexaazatriphenylene hexacarbonitrile in theintermediate connector. Adv Mater, 2008, 20: 324-329？？
[22]
15 Cho T Y, Lin C L, Wu C C. Microcavity two-unit tandem organic light-emitting devices having a high efficiency. Appl Phys Lett, 2006,88: 111106？？
[23]
17 Law C W, Lau K M, Fung M K, et al. Effective organic-based connection unit for stacked organic light-emitting devices. Appl Phys Lett,2006, 89: 133511？？
[24]
19 Zhang H M, Dai Y F, Ma D G, et al. High efficiency tandem organic light-emitting devices with Al/WO3/Au interconnecting layer. ApplPhys Lett, 2007, 91: 123504？？
[25]
21 Chang C C, Chen J F, Hwang S W, et al. Highly efficient white organic electroluminescent devices based on tandem architecture. ApplPhys Lett, 2005, 87: 253501？？
[26]
22 Sun J, Zhu X L, Peng H J, et al. Bright and efficient white stacked organic light-emitting diodes. Org Electron, 2007, 8: 305-310？？
[27]
24 Spindler J P, Hatwar T K. Fluorescent-based tandem white OLEDs designed for display and solid-state-lighting applications. J Soc InfDisplay, 2009, 17: 861-868
[28]
25 Kroger M, Hamwi S, Meyer J, et al. Role of the deep-lying electronic states of MoO3 in the enhancement of hole-injection in organic thinfilms. Appl Phys Lett, 2009, 95: 123301？？
[29]
26 Bao Q Y, Yang J P, Li Y Q, et al. Electronic structures of MoO3-based charge generation layer for tandem organic light-emitting diodes.Appl Phys Lett, 2010, 97: 063303？？
[30]
27 Meyer J, Kroger M, Hamwi S, et al. Charge generation layers comprising transition metal-oxide/organic interfaces: Electronic structureand charge generation mechanism. Appl Phys Lett, 2010, 96: 193302？？
[31]
28 Bao Q Y, Yang J P, Tang J X, et al. Interfacial electronic structures of WO3-based intermediate connectors in tandem organic lightemittingdiodes. Org Electron, 2010, 11: 1578-1583？？
[32]
29 Kang S J, Yi Y, Kim C Y, et al. Energy level diagrams of C60/pentacene/Au and pentacene/C60/Au. Syn Met, 2006, 156: 32-37？？
[33]
30 Kang S J, Yi Y, Kim C Y, et al. Ambipolar organic thin-film transistors using C60/pentacene structure: Characterization of electronicstructure and device property. Appl Phys Lett, 2005, 87: 233502？？
[34]
34 Avilov I, Geskin V, Cornil J. Quantum-chemical characterization of the origin of dipole formation at molecular organic/organic interfaces.Adv Funct Mater, 2009, 19: 624-633？？
[35]
35 Vazquez H, Gao W, Flores F, et al. Energy level alignment at organic heterojunctions: Role of the charge neutrality level. Phys Rev B,2005, 71: 041306？？
[36]
36 Rand B P, Xue J G, Uchida S, et al. Mixed donor-acceptor molecular heterojunctions for photovoltaic applications. I. Material properties.J Appl Phys, 2005, 98: 124902？？
[37]
37 Dimitrakopoulos C D, Mascaro D J. Organic thin-film transistors: A review of recent advances. Ibm J Res Dev, 2001, 45: 11-27？？
