An organic p–n junction as an efficient and cathode independent electron injection layer for flexible inverted organic light emitting diodes

Abstract We demonstrate an organic p–n junction as an efficient electron injection layer for green inverted bottom-emission organic light emitting diodes (IBOLEDs). The organic p–n junction composed of a p-CuPc/n-Bphen layer showed very efficient charge generation under a reverse bias reaching to 100 mA/cm2 at 0.3 V, and efficient electron injection from indium tin oxide (ITO) when adopted in IBOLEDs. Moreover, the organic p–n junction resulted in the same current density–voltage–luminance characteristics independent of the work function of the cathode, which is a valuable advantage for flexible displays.

[1]  K. Walzer,et al.  Highly efficient organic devices based on electrically doped transport layers. , 2007, Chemical reviews.

[2]  M. Baumgarten,et al.  The role of energy level matching in organic solar cells-Hexaazatriphenylene hexacarbonitrile as transparent electron transport material , 2011 .

[3]  Shang-Yu Su,et al.  Flexible inverted bottom‐emitting organic light‐emitting devices with a semi‐transparent metal‐assisted electron‐injection layer , 2010 .

[4]  Yu-Hung Chen,et al.  Electronic structures and electron-injection mechanisms of cesium-carbonate-incorporated cathode structures for organic light-emitting devices , 2006 .

[5]  S. Olthof,et al.  Photoelectron spectroscopy study of systematically varied doping concentrations in an organic semiconductor layer using a molecular p-dopant , 2009 .

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

[7]  H. Bock,et al.  Influence of indium tin oxide treatment using UV–ozone and argon plasma on the photovoltaic parameters of devices based on organic discotic materials , 2006 .

[8]  Ki-Bum Kim,et al.  Homogeneous dispersion of organic p-dopants in an organic semiconductor as an origin of high charge generation efficiency , 2011 .

[9]  K. Fehse,et al.  Energy level alignment of electrically doped hole transport layers with transparent and conductive indium tin oxide and polymer anodes , 2007 .

[10]  Zhuozhi Wang,et al.  Chlorinated Indium Tin Oxide Electrodes with High Work Function for Organic Device Compatibility , 2011, Science.

[11]  William R. Salaneck,et al.  Energy‐Level Alignment at Organic/Metal and Organic/Organic Interfaces , 2009 .

[12]  Bo Qu,et al.  Recent Progresses on Materials for Electrophosphorescent Organic Light‐Emitting Devices , 2011, Advanced materials.

[13]  Stephen R. Forrest,et al.  White Stacked Electrophosphorescent Organic Light‐Emitting Devices Employing MoO3 as a Charge‐Generation Layer , 2006 .

[14]  Mei-Hsin Chen,et al.  Rubidium-Carbonate-Doped 4,7-Diphenyl-1,10-phenanthroline Electron Transporting Layer for High-Efficiency p-i-n Organic Light Emitting Diodes , 2009 .

[15]  Dong-Seok Leem,et al.  Low driving voltage and high stability organic light-emitting diodes with rhenium oxide-doped hole transporting layer , 2007 .

[16]  Chih-I Wu,et al.  A high performance inverted organic light emitting diode using an electron transporting material with low energy barrier for electron injection , 2011 .

[17]  Antje Vollmer,et al.  Optimized hole injection with strong electron acceptors at organic-metal interfaces. , 2005, Physical review letters.

[18]  Toshio Matsumoto,et al.  Bright organic electroluminescent devices having a metal-doped electron-injecting layer , 1998 .

[19]  Fernando Flores,et al.  Doping-induced realignment of molecular levels at organic–organic heterojunctions , 2006 .

[20]  Wei Chen,et al.  Surface transfer doping of semiconductors , 2009 .

[21]  Dong-Seok Leem,et al.  Effectiveness of p-dopants in an organic hole transporting material , 2009 .

[22]  Zhenghong Lu,et al.  Engineering carrier transport across organic heterojunctions by interface doping , 2007 .

[23]  J. Kido,et al.  Hole mobility measurement of 4,4′-Bis[N-(1-naphthyl)-N-phenylamino]-biphenyl by dark injection method , 2011 .

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

[25]  Dongge Ma,et al.  Origin of improvement in device performance via the modification role of cesium hydroxide doped tris(8-hydroxyquinoline) aluminum interfacial layer on ITO cathode in inverted bottom-emission organic light-emitting diodes , 2009 .

[26]  K. Seki,et al.  Energy level alignment and interfacial electronic structures at organic/metal and organic/organic interfaces (vol 11, pg 605, 1999) , 1999 .

[27]  Sei‐Yong Kim,et al.  High efficiency p-i-n top-emitting organic light-emitting diodes with a nearly Lambertian emission pattern , 2009 .

[28]  Yu-Hung Chen,et al.  Electronic and chemical properties of cathode structures using 4,7-diphenyl-1,10-phenanthroline doped with rubidium carbonate as electron injection layers , 2009 .