Fine tuning work function of indium tin oxide by surface molecular design: Enhanced hole injection in organic electroluminescent devices

2001 ◽  
Vol 79 (2) ◽  
pp. 272-274 ◽  
Author(s):  
Chimed Ganzorig ◽  
Kwang-Joo Kwak ◽  
Kazuto Yagi ◽  
Masamichi Fujihira
Keyword(s):  
Work Function ◽  
Tin Oxide ◽  
Indium Tin Oxide ◽  
Molecular Design ◽  
Fine Tuning ◽  
Hole Injection ◽  
Electroluminescent Devices ◽  
Organic Electroluminescent

Chemical modification of indium-tin-oxide electrodes by surface molecular design

2001 ◽  
Vol 708 ◽  
Author(s):  
Chimed Ganzorig ◽  
Masamichi Fujihira
Keyword(s):  
Chemical Modification ◽  
Work Function ◽  
Tin Oxide ◽  
Indium Tin Oxide ◽  
Molecular Design ◽  
Dipole Moments ◽  
Transparent Electrode ◽  
Terminal Group ◽  
Hole Injection ◽  
Oxide Electrodes

ABSTRACTIndium-tin-oxide (ITO) is the most widely used material as a transparent electrode due to its excellent transparency and high conductivity. The devices based on bare ITO, however, exhibited inefficient hole injection due to insufficient high work function and required high drive voltages. Thus, various surface treatments of ITO have been attempted to change the work function of ITO in order to reduce the hole injection barrier height. Electroluminescent (EL) characteristics of devices were improved dramatically using ITO chemically modified with H-, Cl-, and CF3-terminated benzoyl chlorides. By the use of reactive -COCl groups, ITO surfaces were modified quickly and the work function of the modified ITO was changed widely depending upon the permanent dipole moments introduced in p-position of benzoyl chloride. We also compared the performance of the EL devices with ITO modified with different binding groups (-SO2Cl, -COCl, and -PO2Cl2) of p-chlorobenzene derivatives. Finally, we examined the correlation between the change in the work function and the performance of the EL devices by the chemical modification and found that the enormous increase in ITO work function up to 0.9 eV is possible using phenylphosphoryl dichloride with a CF3-terminal group in p-position.

Improvement of Power Efficiency in Organic Electroluminescent Devices

2001 ◽  
Vol 708 ◽  
Author(s):  
Chimed Ganzorig ◽  
Masamichi Fujihira
Keyword(s):  
Work Function ◽  
Indium Tin Oxide ◽  
Power Efficiency ◽  
Dipole Moments ◽  
Electron Injection ◽  
Charge Recombination ◽  
Fine Tuning ◽  
Hole Injection ◽  
Organic Electroluminescent ◽  
Benzoyl Chlorides

ABSTRACTIn order to improve power efficiency of organic electroluminescent (EL) devices, i.e., ITO/TPD/Alq3/Al, enhanced electron and hole injection at Alq3/Al and ITO/TPD interface, respectively, was attempted by designing proper charge injection at both interfaces. Enhanced charge recombination at TPD/Alq3 was also demonstrated. Here, ITO, TPD, Alq3, and Al are abbreviations for indium-tin-oxide, N,N'-diphenyl-N,N'-bis(3-methyl-phenyl)-1,1'-biphenyl-4,4'-diamine, tris(8-hydroxyquinoline) aluminum, and metal aluminum, respectively. Enhanced electron injection by introducing a thin layer of Li salts of fluoride, acetate, and benzoate was described. We have found that the electron injection was improved in the order of Li+, Na+, K+, Rb+, and Cs+, and Cs salts exhibited the best EL performance. Chemical modification of ITO has been attempted to fine-tuning the work function of ITO in order to reduce hole injection barrier height. EL characteristics were improved dramatically using ITO modified with H-, Cl-, and CF3-terminated benzoyl chlorides. By using reactive -COCl groups, ITO surfaces were covered quickly and the work function of ITO was changed widely depending upon permanent dipole moments introduced in para-position of benzoyl chlorides. Correlation between the change in the work function of ITO and the EL characteristics was examined. The improvement of charge recombination was attained by increasing the interfacial areas, i.e. introducing a mixed layer of TPD and Alq3, or inserting a thin film of rubrene with a higher recombination efficiency.

Modulation of indium–tin oxide work function by a versatile self-assembled monolayer measured with the scanning Kelvin nanoprobe

2011 ◽  
Vol 89 (12) ◽  
pp. 1512-1518 ◽  
Author(s):  
Christophe Blaszykowski ◽  
Larissa-Emilia Cheran ◽  
Michael Thompson
Keyword(s):  
Work Function ◽  
Tin Oxide ◽  
Indium Tin Oxide ◽  
Light Emitting Diode ◽  
Critical Role ◽  
Protective Layer ◽  
Organic Coating ◽  
Hole Injection ◽  
Self Assembled Monolayer ◽  
Self Assembling

In molecular optoelectronics, high-quality contacts at electrode|organics interfaces are crucial for charge carriers to efficiently flow through and therefore play a critical role on device performance. Electrode surface morphology, adhesibility, wettability, and work function are thus many parameters that must be accurately controlled, which is achievable using self-assembling monolayer (SAM) surface chemistry. Herein, we employ this technique to alter the electronic and surface energy-related properties of indium–tin oxide (ITO). In comparison to unmodified ITO, the newly introduced SAM-derivatized surface exhibits limited wettability and considerably higher work function (ΔΦ = ~1.2 eV). Several applications are proposed for this organic coating, notably at the anode of organic light-emitting diode (OLED) devices for decreasing the hole injection barrier or as an atmospherically stable protective layer in the coatings industry.

Reduced operating voltage of organic electroluminescent devices by plasma treatment of the indium tin oxide anode

1999 ◽  
Vol 74 (23) ◽  
pp. 3558-3560 ◽  
Author(s):  
F. Steuber ◽  
J. Staudigel ◽  
M. Stössel ◽  
J. Simmerer ◽  
A. Winnacker
Keyword(s):  
Plasma Treatment ◽  
Tin Oxide ◽  
Indium Tin Oxide ◽  
Operating Voltage ◽  
Electroluminescent Devices ◽  
Organic Electroluminescent ◽  
Oxide Anode
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