- Google Home available for Australians from November
- Drone that fits in your pocket
- The technology behind LG TV’s deeper blacks
- Matrox finalist in readers’ choice awards
SELF-organising indium arsenide quantum dots could be used
to construct solar cells, claim a researcher from Tokyo’s University of
Electro-Communications.
According to Professor Koichi Yamaguchi from the University’s
Department of Engineering Science, the quantum dots are produced by exploiting
the Stranski-Krasnov mode of crystal growth.
This results in ordered, highly dense and highly uniform
quantum dots, yielding much better results than the conventional
photolithographic or ‘top-down’ methods widely used for the fabrication of
nano-structures.
Quantum dots have unique opto-electronic properties when
irradiated with light, or under external electromagnetic fields. This makes
them suited for use in lasers, quantum computing and photovoltaic devices.
According to Professor Yamaguchi, the ability to produce
dense arrays of quantum dots was a milestone in enabling the development of semiconducting
quantum dots capable of self-organising themselves for high-efficiency solar
cells.
Professor Yamaguchi and his group also found that indium
arsenide growth at a relatively low substrate temperature of 470 degrees
Celsius on antimonide-irradiated gallium-arsenide layers suppressed the coalescence
of the quantum dots which was observed at higher temperatures.
This allowed the team to use molecular beam epitaxy (MBE) to
grow a layer of indium arsenide quantum dots with a density of 5 x 1011 cm2
on GaAsSb/GaAs (100) substrates.
The potential for photovoltaic device applications was
examined by sandwiching a single layer of indium arsenide quantum dots in a pin-GaAs
cell structure. The resulting external quantum efficiency of these solar cell
structures in the 900 to 1150 nm wavelength range was higher than devices with
the quantum dot layer.
“Theoretical studies suggest QDs solar cells could
yield conversion efficiencies over 50%,” explains Yamaguchi. “This is
a very challenging target but we hope that our innovative approach will be an
effective means of producing such QD based high performance solar cells.”