An array of
nanopillars etched by thin layer of grate-patterned metal creates a
nonreflective yet
conductive surface that could improve electronic device performance.
Image courtesy of
Daniel Wasserman
(December 10, 2015) Light
and electricity dance a complicated tango in devices like LEDs, solar cells and
sensors. A new anti-reflection coating developed by engineers at the University
of Illinois at Urbana Champaign, in collaboration with researchers at the
University of Massachusetts at Lowell, lets light through without hampering the
flow of electricity, a step that could increase efficiency in such devices.
The coating is a specially engraved, nanostructured thin
film that allows more light through than a flat surface, yet also provides
electrical access to the underlying material – a crucial combination for optoelectronics,
devices that convert electricity to light or vice versa. The researchers, led
by U. of I. electrical and computer engineering professor Daniel Wasserman,
published their findings in the journal Advanced Materials.
“The ability to improve both electrical and optical access
to a material is an important step towards higher-efficiency optoelectronic
devices,” said Wasserman, a member of the Micro and Nano Technology Laboratory
at Illinois.
At the interface between two materials, such as a
semiconductor and air, some light is always reflected, Wasserman said. This
limits the efficiency of optoelectronic devices. If light is emitted in a
semiconductor, some fraction of this light will never escape the semiconductor
material. Alternatively, for a sensor or solar cell, some fraction of light
will never make it to the detector to be collected and turned into an
electrical signal. Researchers use a model called Fresnel’s equations to describe
the reflection and transmission at the interface between two materials.