Solar panels suffer from two fundamental problems that have continued to persists even after decades of research: they’re not very efficient, and they cost a lot to produce. At least one of these problems has to be solved before solar power can overtake cheap energy sources like fossil fuels, and some scientists have had their hopes pinned on a common mineral called perovskite. This is an organometal with peculiar light-absorbing properties, and a team of researchers from the University of Sheffield say they’ve figured out how to create high-efficiency perovskite solar cells with a spray painting process. Yes, spray-on solar panels might actually happen.
Perovskite is a crystalline organometal made mostly of calcium titanate, and is found in deposits all over the world. It was first discovered over 150 years ago, but only recently have scientists started investigating its use as a solar panel semiconductor replacement for silicon. It certainly makes sense if we can work out the kinks. Perovskite is considerably cheaper to obtain and process than silicon, and the light absorbing layer can be incredibly thin — about 1 micrometer at minimum versus at least 180 micrometers for silicon. That’s why the spray-on solar panel tech demonstrated by the University of Sheffield is plausible as a real-world solution.
That raises the question, how efficient is this spray-on solar cell? Right now the researchers have managed to eke out 11% efficiency from a thin layer of perovskite. Traditionally manufactured solar cells based on the mineral have reached as high as 19%, and the spray-on variety is expected to reach similar levels eventually. That might not sound very impressive, but nearly 20% efficiency is rather good for an experimental solar panel. The average efficiency of silicon cells is only 25% after all. Other materials claim higher numbers, but they aren’t nearly ready for use.
The breakthrough here is in the process of applying perovskite in a thin uniform layer so it can efficiently 
absorb light on almost any surface. A layer of this material could be used as the basis for solar panels on cars or mobile devices that don’t have completely flat surfaces for mounting standard solar panels — the structure and properties of crystalline silicon simply don’t allow for very much flexibility. A solar panel on your phone? Sure, why not? However, the University of Sheffield team cautions the efficiency of spray-on perovskite will decrease a bit on curved surfaces. [DOI: 10.1039/C4EE01546K – “Efficient planar heterojunction mixed-halide perovskite solar cells deposited via spray-deposition”]
The spray-on process has several key benefits in addition to the obvious non-flat solar cells. Most importantly, it should be incredibly easy to scale up — or down for that matter. The same nozzle can be used to manufacture a small solar panel for personal electronics and a large one for a car. It’s just about the number of passes it takes to coat the surface. The perovskite solution used can also be mass produced cheaply and is easier to handle than silicon. This all combines to lower the potential cost of solar power considerably.
Perovskite is nearing the point that it could actually supplant silicon as the standard for solar panel tech. In just a few years these panels have gone from low single digit efficiencies to nearly matching silicon. This might finally be the breakthrough we’ve been waiting for to move renewable energy forward.