New Connection between Stacked Solar
Cells Can Save on Wasted Energy
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Researchers have come up with a new technique for improving the
connections between stacked solar cells, which should improve the overall
efficiency of solar energy devices and reduce the cost of solar energy
production.
The new connections can allow these cells to operate at solar
concentrations of 70,000 suns worth of energy without losing much voltage as
"wasted energy" or heat.
Stacked solar cells consist of several solar cells that are
stacked on top of one another. Stacked cells are currently the most efficient
cells on the market, converting up to 45 percent of the solar energy they
absorb into electricity.
But to be effective, solar cell designers need to ensure the
connecting junctions between these stacked cells do not absorb any of the solar
energy and do not siphon off the voltage the cells produce - effectively
wasting that energy as heat.
Researchers discovered that by inserting a very thin film of
gallium arsenide into the connecting junction of stacked cells we can virtually
eliminate voltage loss without blocking any of the solar energy.
This work is important because photovoltaic energy companies are
interested in using lenses to concentrate solar energy, from one sun (no lens)
to 4,000 suns or more. But if the solar energy is significantly intensified -
to 700 suns or more - the connecting junctions used in existing stacked cells
begin losing voltage. And the more intense the solar energy, the more voltage
those junctions lose - thereby reducing the conversion efficiency.
We have created a connecting junction that loses almost no
voltage, even when the stacked solar cell is exposed to 70,000 suns of solar
energy. And that is more than sufficient for practical purposes, since
concentrating lenses are unlikely to create more than 4,000 or 5,000 suns worth
of energy. This discovery means that solar cell manufacturers can now create
stacked cells that can handle these high-intensity solar energies without
losing voltage at the connecting junctions, thus potentially improving
conversion efficiency.
This should reduce overall costs for the energy industry because,
rather than creating large, expensive solar cells, you can use much smaller
cells that produce just as much electricity by absorbing intensified solar
energy from concentrating lenses. And concentrating lenses are relatively
inexpensive.
