Electroluminescence from single monolayers of nanocrystals in molecular organic devices

Publication Type:

Journal Article

Source:

Nature, nature.com, Volume 420, Issue 6917, p.800-803 (2002)

ISBN:

0028-0836

Keywords:

2002, 2013 and earlier

Abstract:

The integration of organic and inorganic materials at the nanometre scale into hybrid optoelectronic structures enables active devices that combine
the diversity of organic materials with the high-performance electronic
and optical properties of inorganic nanocrystals. The optimization of such
hybrid devices ultimately depends upon the precise positioning of the
functionally distinct materials. Previous studies have already emphasized
that this is a challenge, owing to the lack of well-developed
nanometre-scale fabrication techniques. Here we demonstrate a hybrid
light-emitting diode (LED) that combines the ease of processability of
organic materials with the narrow-band, efficient luminescence of
colloidal quantum dots (QDs). To isolate the luminescence processes from
charge conduction, we fabricate a quantum-dot LED (QD-LED) that contains
only a single monolayer of QDs, sandwiched between two organic thin films.
This is achieved by a method that uses material phase segregation between
the QD aliphatic capping groups and the aromatic organic materials. In our
devices, where QDs function exclusively as lumophores, we observe a
25-fold improvement in luminescence efficiency (1.6 cd A(-1) at 2,000 cd
m(-2)) over the best previous QD-LED results. The reproducibility and
precision of our phase-segregation approach suggests that this technique
could be widely applicable to the fabrication of other hybrid
organic/inorganic devices.