Air-Stable, Cross-Linkable, Hole-Injecting/Transporting Interlayers for Improved Charge Injection in Organic Light-Emitting Diodes
Modification of inorganic electrode surfaces has attracted great attention in the quest to optimize organic optoelectronic devices. An air-stable, cross-linkable trimethoxysilane functionalized hole-transporting triarylamine (4,4'-bis[(p-trimethoxysilylpropylphenyl)phenylamino]biphenyl, TPD-[Si(OMe)3]2) has been synthesized and self-assembled or spin-coated onto tin-doped indium oxide (ITO) anode surfaces to form monolayers or multilayer siloxane films, respectively. The modified ITO surfaces were characterized by advancing aqueous contact angle, X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and cyclic voltammetry (CV). Increased surface work function and enhanced ITO-hole transport layer (HTL) contact via robust covalent bonding are expected to facilitate hole injection from the ITO anode, resulting in organic light-emitting diode (OLED) performance enhancement versus that of a device without such interlayers. For a device having the structure ITO/spin-coated-TPD-[Si(OMe)3]2 from aqueous alcohol + acetic acid blend solution (40 nm)/NPB (20 nm)/Alq (60 nm)/LiF (1 nm)/Al (100 nm), a maximum light output of 32800 cd/m2, a 4.25 V turn-on voltage, and a maximum current efficiency of 5.8 cd/A is achieved. This performance is comparable to or superior to that of analogous devices prepared with analogous trichorosilyl precursors. The air-stable interlayer material developed here is also applicable to large-area coating techniques.
- Research Organization:
- Brookhaven National Lab. (BNL), Upton, NY (United States). National Synchrotron Light Source
- Sponsoring Organization:
- Doe - Office Of Science
- DOE Contract Number:
- DE-AC02-98CH10886
- OSTI ID:
- 959645
- Report Number(s):
- BNL-82631-2009-JA; CMATEX; TRN: US1005771
- Journal Information:
- Chemistry of Materials, Vol. 20, Issue 15; ISSN 0897-4756
- Country of Publication:
- United States
- Language:
- English
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