THIN-FILM PHOTOVOLTAICS
Conventional crystalline silicon technologies (x-Si) require considerable amounts
of expensive material with additional complexity and costs needed to wire individual cells together. Competing technologies, however, are based on depositing
extremely thin films of photovoltaic materials onto glass or metal substrates.
Thin-film devices use relatively little material (their thickness is in the micron
range rather than the hundreds-of-microns range needed by crystalline silicon) they do not require the complexity of cell interconnections, and they are particularly well suited to mass-production techniques. Their thinness allows photons
that aren’t absorbed to pass completely through the photovoltaic material, which
offers two special opportunities. Their semitransparency means that they can
be deposited onto windows, making building glass a provider of both light and electricity. They also lend themselves to multiple-junction, tandem cells in which
photons of different wavelengths are absorbed in different layers of the device In exchange for these highly desirable properties, thin-film cells are not as
efficient as x-Si—especially when they are not used in tandem devices. While
the likelihood of significant reductions in module costs are modest for conventional crystalline silicon, many opportunities remain to increase efficiency and
dramatically reduce costs using thin-film technologies. Many believe that thin
films will be the dominant photovoltaic technology in the future