In the global search for sustainable energy sources,
photovoltaic (PV) cells are an area of keen interest because of
their ability to convert absorbed sunlight to electricity
through the interactions of photons (packets of light) and
electrons in a semiconducting material. In 1954 Bell Labs
introduced the first modern silicon-based PV cells, but with
production costs more than $1,000 per kilowatt, their use was
limited. Flash forward more than 50 years, and the cost of
producing PV cells now is around $4 per kilowatt, and their use,
though not widespread, is more commonplace. Today PV systems
power communication and navigation equipment, light homes and
commercial buildings, and feed electricity back into the utility
grid. The sun radiates more energy in a single hour than the
entire planet uses in a whole year, yet solar energy provides
less than 1 percent of the world’s electricity. Although
sunlight is free, PV-generated electricity costs about 5 times
more than grid electricity. Conventional PV cells are