have found a way to augment ordinary silicon solar cells with a material called
a perovskite. Putting a new kind of photovoltaic material on top of a
conventional solar cell can boost overall power output by half. Researchers at
Stanford University added a type of material known as a perovskite to a silicon
solar cell, validating an idea for cheaply increasing the efficiency of solar
power that was first proposed several years ago.
are materials with a particular crystalline structure. The perovskite used by
the Stanford team contains relatively abundant and cheap materials including
ammonia, iodine, and lead. Materials scientists started demonstrating the
photovoltaic potential of perovskites in 2009. Since then, different research
groups have created perovskites with photovoltaic efficiencies comparable to
those of many commercial solar cells. But perovskites also convert certain
parts of the solar spectrum into electricity more efficiently than silicon, and
vice versa, so the biggest efficiency gain may come from using perovskites to
augment, rather than replace, the silicon in most solar cells (see “A Material
that Could Make Solar Power ‘Dirt Cheap’ and “What’s Tech is Next for the Solar
Industry?”). Now researchers at Stanford have shown that the idea can work.
of the main challenges with pairing perovskite cells with silicon ones has been
rendering the former transparent, so that light they don’t absorb can pass
through to the silicon cells beneath. The perovskite solar cells made
previously used an opaque material on the back to collect electrical current.
The Stanford researchers developed a manufacturing method that involves
producing a transparent electrode made of silicon nanowires. The researchers
took a cheap silicon solar cell with an efficiency of 11.4 percent and
increased it to 17 percent by adding the perovskite cell.
work remains to be done before such cells are ready for market, however.
Perovskite cells currently don’t last very long, and researchers are still
trying to develop versions that don’t use lead, which is toxic. The way light
interacts with the two materials is also not yet well understood. When the
Stanford group added perovskite to silicon solar cells whose efficiency was
already 17 percent, for example, they measured a much smaller increase in power
output, to 17.9 percent. Even so, perovskites could be a boon for the solar
industry. The researchers believe that perovskite-silicon cells will convert
over 30 percent of the energy in sunlight into electricity. Such a boost would
cut the number of solar panels for some installations almost in half, greatly
lowering installation costs. (Source: MIT)