The metal interlayer in the charge generation layer of tandem organic light-emitting diodes

This work studies the interface in the charge generation layer (CGL), consisting of aluminum (Al) doped in poly(ethylene glycol) dimethyl ether as an n-type layer and 2, 3, 5, 6-tetrafluoro-7, 7, 8, 8-tetracyanoquinodimethane (F4-TCNQ) doped in N,N′-bis-(1-naphthyl)-N,N′-diphenyl-1,1′-biphenyl-4-4′-diamine as an p-type layer, in tandem organic light-emitting diodes (OLEDs). Introducing a thin high work function metal interlayer (e.g., Ag or Au) effectively improves the transport and inhibits the accumulation of charges in the CGL, which markedly reduces the operating voltage and enhances the efficiency of tandem OLEDs. We attribute that the high density of surface states on metal clusters (interlayer) reduce the junction barrier to facilitate the transport of carriers through CGL. Experimental results show enhancements of tandem OLEDs by an additional metal interlayer as follows: luminous efficiency increases from 37.2 to 51.4 cd A−1, the light turn-on voltage decreases from 9.2 to 6.6 V, and luminescence at 10 mA cm−2 increases from 3712 to 5211 cd m−2.

[1]  Handong Sun,et al.  Silver nanoparticle facilitated charge generation in tandem organic light-emitting devices , 2013 .

[2]  Jong‐Lam Lee,et al.  Charge Generation Mechanism of Metal Oxide Interconnection in Tandem Organic Light Emitting Diodes , 2012 .

[3]  T. Wen,et al.  Poly(ethylene oxide)-functionalized Al cathodes of tunable electron-injection capabilities for efficient polymer light-emitting diodes , 2011 .

[4]  T. Wen,et al.  The Roles of Poly(Ethylene Oxide) Electrode Buffers in Efficient Polymer Photovoltaics , 2011 .

[5]  A. Kahn,et al.  The Role of Transition Metal Oxides in Charge‐Generation Layers for Stacked Organic Light‐Emitting Diodes , 2010 .

[6]  Shui-Tong Lee,et al.  Interface studies of intermediate connectors and their roles in tandem OLEDs , 2010 .

[7]  T. Sakurai,et al.  Influence of gap states on electrical properties at interface between bathocuproine and various types of metals , 2010 .

[8]  T. Wen,et al.  White-emissive tandem-type hybrid organic/polymer diodes with (0.33, 0.33) chromaticity coordinates. , 2009, Optics express.

[9]  T. Wen,et al.  Organic‐Oxide Cathode Buffer Layer in Fabricating High‐Performance Polymer Light‐Emitting Diodes , 2008 .

[10]  X. D. Gao,et al.  Mechanism of charge generation in p -type doped layer in the connection unit of tandem-type organic light-emitting devices , 2008 .

[11]  G. Kushto,et al.  Electronic structure and morphology of organic/metal/organic junctions , 2008 .

[12]  Tae-Woo Lee,et al.  High-efficiency stacked white organic light-emitting diodes , 2008 .

[13]  L. Liao,et al.  Tandem Organic Light‐Emitting Diode using Hexaazatriphenylene Hexacarbonitrile in the Intermediate Connector , 2008 .

[14]  Chun-Sing Lee,et al.  Influences of Connecting Unit Architecture on the Performance of Tandem Organic Light‐Emitting Devices , 2007 .

[15]  M. Wong,et al.  Bright and efficient white stacked organic light-emitting diodes , 2007 .

[16]  T. Riedl,et al.  Temperature-independent field-induced charge separation at doped organic/organic interfaces: Experimental modeling of electrical properties , 2007 .

[17]  Tetsuo Tsutsui,et al.  Electric-field-assisted bipolar charge generation from internal charge separation zone composed of doped organic bilayer , 2007 .

[18]  T. Wen,et al.  Organic oxide/Al composite cathode in small molecular organic light-emitting diodes , 2006 .

[19]  S. Forrest,et al.  Stacked white organic light-emitting devices based on a combination of fluorescent and phosphorescent emitters , 2006 .

[20]  Yang Yang,et al.  Effective connecting architecture for tandem organic light-emitting devices , 2005 .

[21]  T. Wen,et al.  High-performance polymer light-emitting diodes utilizing modified Al cathode , 2005 .

[22]  Jun Endo,et al.  27.5L: Late‐News Paper: Multiphoton Organic EL device having Charge Generation Layer , 2003 .

[23]  Kahn,et al.  Chemistry and electronic properties of metal-organic semiconductor interfaces: Al, Ti, In, Sn, Ag, and Au on PTCDA. , 1996, Physical review. B, Condensed matter.