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Tuning the Work Function of Polar Zinc Oxide Surfaces using Modified Phosphonic Acid Self‐Assembled Monolayers
Author(s) -
Lange Ilja,
Reiter Sina,
Pätzel Michael,
Zykov Anton,
Nefedov Alexei,
Hildebrandt Jana,
Hecht Stefan,
Kowarik Stefan,
Wöll Christof,
Heimel Georg,
Neher Dieter
Publication year - 2014
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.201401493
Subject(s) - materials science , monolayer , work function , self assembled monolayer , zinc , electrode , semiconductor , nanotechnology , optoelectronics , oxide , kelvin probe force microscope , polar , layer (electronics) , chemical engineering , atomic force microscopy , chemistry , physics , astronomy , engineering , metallurgy
Zinc oxide (ZnO) is regarded as a promising alternative material for transparent conductive electrodes in optoelectronic devices. However, ZnO suffers from poor chemical stability. ZnO also has a moderate work function (WF), which results in substantial charge injection barriers into common (organic) semiconductors that constitute the active layer in a device. Controlling and tuning the ZnO WF is therefore necessary but challenging. Here, a variety of phosphonic acid based self‐assembled monolayers (SAMs) deposited on ZnO surfaces are investigated. It is demonstrated that they allow the tuning the WF over a wide range of more than 1.5 eV, thus enabling the use of ZnO as both the hole‐injecting and electron‐injecting contact. The modified ZnO surfaces are characterized using a number of complementary techniques, demonstrating that the preparation protocol yields dense, well‐defined molecular monolayers.