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Volume: 17 | Article ID: art00019_2
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ITO Modification for More Efficient Hole Injection in Organic Light Emitting Diodes
Yulong Shen
Ken Diest
George Malliaras
  DOI :  10.2352/ISSN.2169-4451.2001.17.1.art00019_2  Published Online :  January 2001
Abstract

Indium Tin Oxide is the most commonly used anode electrode in organic light emitting diodes (OLEDs). A critical parameter for charge injection is its workfunction, varies between 4.5 and 5.1 eV, depending on the sample preparation and cleaning procedure. These large variations in the workfunction translate to even larger variations in the injected current, which is a major issue for the fabrication of efficient OLEDs. We demonstrate a way to treat ITO and get a contact with good injection characteristics, regardless of the ITO preparation procedure. We have carried out direct measurements of the injection efficiency at the ITO/TPD contact (TPD is N-N'-diphenyl-N-N'-bis(3-methylphenyl)-1-1-biphenyl-4,4'-diamine, a commonly used hole transport layer). The contact is found to be current-limiting, supplying TPD only with 1% of the space charge limited current. By introducing a thin layer of polyaniline, or a thin film of a high work function metal, the injection efficiency approaches 100%, i.e. the contact becomes Ohmic. The performance of the contact shows little sensitivity to the details of the ITO preparation. A mechanism for this improvement is proposed. The change in the characteristics of TDP-based OLEDs are discussed.

Journal Title : NIP & Digital Fabrication Conference
Publisher Name : Society of Imaging Science and Technology
Publisher Location : 7003 Kilworth Lane, Springfield, VA 22151, USA
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 DOI 10.2352/ISSN.2169-4451.2001.17.1.art00019_2
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Yulong Shen, Ken Diest, George Malliaras, "ITO Modification for More Efficient Hole Injection in Organic Light Emitting Diodes"  in Proc. IS&T Int'l Conf. on Digital Printing Technologies (NIP17),  2001,  pp 531 - 531,  https://doi.org/10.2352/ISSN.2169-4451.2001.17.1.art00019_2

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Copyright © Society for Imaging Science and Technology 2001
72010410
NIP & Digital Fabrication Conference
nip digi fabric conf
2169-4451
Society of Imaging Science and Technology
7003 Kilworth Lane, Springfield, VA 22151, USA
2169-4451(20010101)2001:2L.531;1-
nip_v2001n2/splitsection19.xml
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Articles
ITO Modification for More Efficient Hole Injection in Organic Light Emitting Diodes
ShenYulong
DiestKen
MalliarasGeorge
01012001
2001
2
531
531
2001
Indium Tin Oxide is the most commonly used anode electrode in organic light emitting diodes (OLEDs). A critical parameter for charge injection is its workfunction, varies between 4.5 and 5.1 eV, depending on the sample preparation and cleaning procedure. These large variations in the workfunction translate to even larger variations in the injected current, which is a major issue for the fabrication of efficient OLEDs. We demonstrate a way to treat ITO and get a contact with good injection characteristics, regardless of the ITO preparation procedure. We have carried out direct measurements of the injection efficiency at the ITO/TPD contact (TPD is N-N'-diphenyl-N-N'-bis(3-methylphenyl)-1-1-biphenyl-4,4'-diamine, a commonly used hole transport layer). The contact is found to be current-limiting, supplying TPD only with 1% of the space charge limited current. By introducing a thin layer of polyaniline, or a thin film of a high work function metal, the injection efficiency approaches 100%, i.e. the contact becomes Ohmic. The performance of the contact shows little sensitivity to the details of the ITO preparation. A mechanism for this improvement is proposed. The change in the characteristics of TDP-based OLEDs are discussed.