Efficient
Electron Injection by Size- and Shape-Controlled Zinc Oxide Nanoparticles
in Organic Light-Emitting Devices
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Abstract
Three
different sized zinc oxide (ZnO) nanoparticles were synthesized as
spherical ZnO (S-ZnO), rodlike ZnO (R-ZnO), and intermediate shape
and size ZnO (I-ZnO) by controlling the reaction time. The average
sizes of the ZnO nanoparticles were 4.2 nm × 3.4 nm for S-ZnO,
9.8 nm × 4.5 nm for I-ZnO, and 20.6 nm × 6.2 nm for R-ZnO.
Organic light-emitting devices (OLEDs) with these ZnO nanoparticles
as the electron injection layer (EIL) were fabricated. The device
with I-ZnO showed lower driving voltage and higher power efficiency
than those with S-ZnO and R-ZnO. The superiority of I-ZnO makes it
very effective as an EIL for various types of OLEDs regardless of
the deposition order or method of fabricating the organic layer, the
ZnO layer, and the electrode