TECH FOCUS SOLAR
Souped-up solar absorption with perovskites
Perovskite solar cell design delivers efficiencies to rival those made of silicon
R
esearchers at MIT have developed a fresh approach to designing
perovskite solar cells that pushes the material to match, and even exceed, the efficiency of typical silicon solar cells used today. Perovskites are a leading candidate for eventually replacing silicon as the material of choice for solar panels. They offer the potential for low-cost, low-temperature manufacturing of ultrathin, lightweight flexible cells, but so far their efficiency at converting sunlight to electricity has lagged behind that of silicon and some other alternatives. While silicon solar cells offer efficiency ranging from 20 to 22 per cent, the MIT scientists have boosted the efficiency of perovskite as a solar cell to 25.2 per cent, which they say has laid the groundwork for further improvements in the future. The efficiency boost, which eclipses that of many existing solar panels, was achieved by modifying the perovskite formula, as well as adding a specially treated conductive layer of tin dioxide bonded to the perovskite material, which provides an improved path for the charge carriers in the cell. The findings are described in a paper in Nature.
A strong contender Perovskites are a broad class of materials defined by the fact that they have a particular
24 Electro Optics April 2021
kind of molecular arrangement, or lattice, that resembles that of the naturally occurring mineral perovskite. There are vast numbers of possible chemical combinations that can make perovskites, with these materials attracting worldwide interest due to them being, at least on paper, much cheaper to produce than silicon or gallium arsenide (one of the other leading material contenders for solar cells). This is partly because they are much simpler to manufacture and process, as to produce and process silicon or gallium arsenide, sustained heat of over 1,000°C is required.
“We can make efficiencies that threaten silicon, and hopefully within punching distance of
gallium arsenide”
In contrast, perovskites can be processed at less than 200°C, either in solution or by vapour deposition. The other major advantage of
perovskite over silicon, or many other candidate replacements, is that it forms extremely thin layers while still efficiently capturing solar energy. ‘Perovskite cells have the
potential to be lightweight compared to silicon, by orders of magnitude,’ said Moungi Bawendi, a professor of
chemistry at MIT and an author of the Nature paper. Perovskites have a higher
bandgap than silicon, which means they absorb a different part of the light spectrum and thus can complement silicon cells to provide even greater combined efficiencies. But even using only perovskite, according to co-author Jason Yoo, ‘what we’re demonstrating is that even with a single active layer, we can make efficiencies that threaten silicon, and
hopefully within punching distance of gallium arsenide. And both of those technologies have been around for much longer than perovskites have.’
Layered development One of the keys to the team’s improvement of the material’s efficiency, Bawendi explained, was in the precise engineering of one layer of the sandwich that makes up a perovskite solar cell – the electron transport layer. The
@electrooptics |
www.electrooptics.com
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38
