The price of silicon-based solar panels is already falling fast, and solar installers are looking at ways to bring down "soft costs" too.

But researchers are now looking to identify the next generation of solar panels, which may trade decreases in efficiency for greatly reduced pricing. The common mineral perovskite has been touted as a way to build cheaper, dye-sensitized solar cells. In fact, the National Renewable Energy Laboratory recently reported significant advances in perovskite-based solar cell efficiency:

In four years, perovskite's conversion efficiency — the yield at which the photons that hit the material are turned into electrons that can be used to generate electricity — has grown from 3.8% in 2009 to just north of 16%, with unconfirmed reports of even higher efficiencies arriving regularly. That's better than a four-fold increase. By contrast, efficiencies of single-crystal solar cells grew by less than 50% during their first five years of development, and most other types of solar cells showed similar modest improvements during their first few years.
There are, however, drawbacks. Early perovskite-based solar cells used lead — a material that is not without its environmental drawbacks — as the light-absorbing layer. Now researchers at Northwestern University have developed a new form of perovskite-based solar cell that replaces lead with tin, a commonly available and much more benign material. The efficiency of this early tin-based cell is a just below 6 percent, but researchers believe there is no reason that tin perovskite solar shouldn't achieve much greater efficiencies on a par with lead:
The new solar cell uses a structure called a perovskite but with tin instead of lead as the light-absorbing material. Lead perovskite has achieved 15 percent efficiency, and tin perovskite should be able to match — and possibly surpass that. Perovskite solar cells are being touted as the "next big thing in photovoltaics" and have reenergized the field.
Tantalizingly, the press release from Northwestern suggests these new cells can be made using "bench" chemistry — meaning no fancy equipment or hazardous materials are necessary. If true, that really could be a game changer.

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Could tin create cheap, efficient solar cells?
There are 2 ways to make solar mainstream: increase efficiency or lower costs. Tin-based solar cells may achieve the latter.