Enlarge / Some solar panels, along with a diagram of a perovskite's crystal structure. (credit: Subhakitnibhat Kewiko)

As the price of silicon panels has continued to come down, we've reached the point where they're a small and shrinking cost of building a solar farm. That means that it might be worth spending more to get a panel that converts more of the incoming sunlight to electricity, since it allows you to get more out of the price paid to get each panel installed. But silicon panels are already pushing up against physical limits on efficiency. Which means our best chance for a major boost in panel efficiency may be to combine silicon with an additional photovoltaic material.

Right now, most of the focus is on pairing silicon with a class of materials called perovskites. Perovskite crystals can be layered on top of silicon, creating a panel with two materials that absorb different areas of the spectrum—plus, perovskites can be made from relatively cheap raw materials. Unfortunately, it has been difficult to make perovskites that are both high-efficiency and last for the decades that the silicon portion will.

Lots of labs are attempting to change that, though. And two of them reported some progress this week, including a perovskite/silicon system that achieved 34 percent efficiency.

Enlarge / All these pieces more or less pop apart after a brief chemical treatment. (credit: Israel Sebastian.)

For years, the arguments against renewable power focused on its high costs. But as the price of wind and solar plunged, the arguments shifted. Suddenly, concerns about the waste left behind when solar panels hit end-of-life became so common that researchers at the US's National Renewable Energy Lab felt compelled to publish a commentary in Nature Physics debunking them.

Part of the misinformation is pure nonsense. The primary ingredients of most panels are silicon, aluminum, and silver, none of which is a major environmental threat. Solar panels also have a useful lifespan of decades, and the vast majority of those in existence are less than 10 years old, so waste hasn't even become much of a problem yet. And, even once these panels age out, recycling techniques are available.

Perhaps the only realistic concern is that existing recycling technologies rely on nitric acid and can produce some toxic waste. But a group of researchers from Wuhan University have figured out an alternative means of recycling that avoids the production of toxic waste and is more energy-efficient as a bonus.