College of Illinois
Scientists Present Us Little Known Methods to Produce More Effective
Photo voltaic panels
Although silicon is actually the industry standard semiconductor in
almost all electronic products, including the pv cells that sun panels
utilize to convert sun rays into energy, it is not really the most
cost-efficient material available. For example, the semiconductor
gallium arsenide and similar substance semiconductors provide nearly
double the efficiency as silicon in solar units, yet they are rarely
utilized in utility-scale applications because of their excessive
production price.
U. of I.
teachers J. Rogers and X. Li investigated lower-cost techniques to
produce thin films of gallium arsenide which also granted flexibility in
the types of devices they could be incorporated into.
If you can minimize significantly the cost of gallium arsenide and some
other compound semiconductors, then you could develop their variety of
applications.
Generally, gallium arsenide is transferred in a individual thin layer on
a smaller wafer. Either the desired device is produced directly on the
wafer, or the semiconductor-coated wafer is break up into chips of the
ideal size. The Illinois team made the decision to put in several layers
of the material on a simple wafer, creating a layered, “pancake” stack
of gallium arsenide thin films.
If you increase ten levels in 1 growth, you only have to load the wafer
one time. If you do this in 10 growths, loading and unloading with heat
range ramp-up and ramp-down get a lot of time. If you take into account
what is necessary for each growth – the equipment, the research, the
period, the workers – the overhead saving this solution offers is a
significant expense reduction.
Next the researchers separately peel off the levels and move them. To
achieve this, the stacks swap levels of aluminum arsenide with the
gallium arsenide. Bathing the stacks in a formula of acid and an
oxidizing agent dissolves the layers of aluminum arsenide, freeing the
single thin sheets of gallium arsenide. A soft stamp-like system selects
up the layers, one at a time from the top down, for shift to another
substrate – glass, plastic-type or silicon, based on the application.
Then the wafer could be reused for an additional growth.
By executing this it's possible to create significantly more material a
lot more rapidly and much more cost efficiently. This process could
create bulk amounts of material, as opposed to merely the thin
single-layer manner in which it is usually grown.
Freeing the material from the wafer also opens the possibility of
flexible, thin-film electronics produced with gallium arsenide or some
other high-speed semiconductors. To make devices that can conform but
still retain high efficiency, that’s considerable.
In a document released online May twenty in the publication
Nature, the group
details its procedures and demonstrates 3 types of products using
gallium arsenide chips manufactured in multilayer stacks: light devices,
high-speed transistors and photo voltaic cells. The authors also supply
a detailed price evaluation.
An additional advantage of the multilayer approach is the release from
area constraints, particularly essential for photo voltaic cells. As the
levels are eliminated from the stack, they may be laid out side-by-side
on another substrate in order to produce a significantly larger surface
area, whereas the typical single-layer procedure confines area to the
size of the wafer.
For solar panels, you need large area coverage to catch as much sunshine
as possible. In an extreme case we may increase sufficient levels to
have ten times the area of the traditional.
Up coming, the team plans to investigate more prospective device
applications and additional semiconductor resources that could adapt to
multilayer growth.
The best visible signal of
worldwide global warming: the melting away of glaciers in the Alps.
In the summer of 2003, for
example, the “eternal ice cap” of the Alps lost five to ten percent of its
volume. A unique type of landscape is threatened in its existence. Do we
belong to the last generation that can admire the magnificent giants of
ice?
This first picture is the
view from the Gornergrat, above Zermatt in Switzerland. The red arrows
show the line of how high the glaciers once reached at this location
These 3 images show the
Rhone Glacier, first 2 taken around 1914 and the last one from September
2006 and you clearly see by comparing the last to pictures of how much the
ice has receded, as the new image shows all of the lower part of that
glacier is completely gone, showing only the carved stones left behind.
TheGuardian — October 15,
2008 — Glaciers in the Tian Mountains in western China are melting
because of global warming. Jonathan Watts went to see how this affects
local people:
With
the melting of the glaciers along comes the melting of the so called
permafrost, the earth and stones layers that where permanently frozen,
with the melting away we see more erosion going on putting at risk many
alpine villages and infrastructures like roads and railways etc. On the
other side the glaciers are today a reservoir for water giving it up
slowly in summertime but once gone there will be no more reservoir and
many rivers my dry out.
For more on the effects on
global warming on the glaciers see also: "
Wo sind
unsere Gletscher " and the exhibition Glaciers in the Hothouse at the
Swiss Alpine Museum.
And
here this article in German from Siegel Online: Schweizer Alpen nicht
mehr winterfest.
Planet Under Pressure
With humanity demanding more from the Earth than ever
before, BBC News explores the planet's most pressing environmental
problems in a six-part series.
Click here for this series from BBC.
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With
the melting of the glaciers along comes the melting of the so called
permafrost, the earth and stones layers that where permanently frozen,
with the melting away we see more erosion going on putting at risk many
alpine villages and infrastructures like roads and railways etc. On the
other side the glaciers are today a reservoir for water giving it up
slowly in summertime but once gone there will be no more reservoir and
many rivers my dry out.