A brand new design could see cheap yet high-performance solar cells manufactured from everyday materials. Engineers at Stanford and Oxford universities have developed a new type of solar cell, which could even outperform traditional silicon cells.
Solar cells work by collecting light energy from the sun and converting it into an electrical current. In a conventional cell, a layer of silicon crystals absorbs light energy from the sun. This causes electrons to become excited to the point that they are ejected from the material. We can capture the resulting electric current for use as clean electricity.
Engineers from Stanford and Oxford have found a way to produce a new light capturing material using tin and other common elements. ‘Perovskite’ works in a similar way to silicon cells. The difference: it is thinner, more flexible and easier to manufacture than silicon crystals.
Michael McGehee is co-author of the study and professor of materials science and engineering at Stanford. Speaking about their development he said: “Perovskite semiconductors have shown great promise for making high efficiency solar cells at low cost.” He went on to state that their device captures and converts 20.3 percent of sunlight that hits it. This efficiency is comparable to the silicon solar cells currently in use.
The device that the researchers have made is built by stacking two perovskite solar cells in tandem. At the moment, the crystals are printed onto glass, however the same technology could also print cells onto plastics. Henry Snaith, co-author and a professor of physics at Oxford, was confident in the success of the device. He said: “The all-perovskite tandem cells we have demonstrated clearly outline a roadmap for thin-film solar cells to deliver over 30 percent efficiency. This is just the beginning.”
As well as increasing the efficiency of the cells in action, the new device can cut both cost and energy in manufacturing. To create the silicon crystals for a conventional panel, silica rock must be heated to over 1,600 degrees Celsius. Perovskite crystals can be produced in a lab from common materials such as lead, tin and bromine. They can even be printed directly onto glass at room temperature.
Building the device, however, was not the biggest challenge the team faced.
One of the major concerns with perovskite is its stability. A typical silicon solar panel has a lifespan of around 25 years or more. Perovskites are much less stable and can degrade quickly when exposed to light or water, which is not ideal in a solar panel. To make their device usable, the team had to create a stable perovskite that could capture enough sunlight and produce a decent voltage.
To test the composition of their material, the team exposed the cells to 100-degree heat for four days straight. Now they are confident the material is stable, the next step is maximising light absorption and increasing the currents.
Image credit: L.A. Cicero.
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