For some, pervoskite research remains the holy grail of the solar industry, inciting deep intrigue with the promise of heightened efficiencies by adding just a thin extra layer to a solar cell. However, as with everything that seems to good to be true, there is one major hurdle, and in the case of perovskites it is stability and durability.
Researchers at Stanford and Oxford believe that they might have solved this problem, and created an even better product, by removing the silicon cell altogether. The scientists, reported in the most recent edition of Science, have created a solar cell that replaces the silicon cell with one made of perovskite crystal instead. So, instead of adding a thin layer of perovskites on top of a silicon cell to increase efficiency, which is where most of the prominent research is currently focused, this method uses purely perovskite crystal to construct the cell.
The perovskite crystal can be made with tin or with any other abundant elements, and is printed on glass, but can even be done on plastic. Two cells are then stacked next to each other, working in tandem to generate electricity from solar energy.
Perovskite cells can be processed in a laboratory from common materials like lead, tin and bromine, then printed on glass at room temperature, explained postpoctoral scholar at Stanford and co-lead author of the report Tom Leijtens.
The same efficiency for a lower cost
Being able to use these materials instead of silicon, of course, much reduces the production cost of the cell. Incredibly, the research team was able to create efficiency levels similar to those created by silicon cells, with the highest efficiency recorded for the new device set at 20.3%.
Perovskite semiconductors have shown great promise for making high-efficiency solar cells at low cost, commented Stanford professor and co-author of the study Michael McGhee. We have designed a robust, all-perovskite device that converts sunlight into electricity with an efficiency of 20.3%, a rate comparable to silicon solar cells on the market today. The efficiency of our tandem device is already far in excess of the best tandem solar cells made with other low-cost semiconductors, such as organic small molecules and microcrystalline silicon.
Of course, the question of stability and durability appeared again, but the team of scientists think that they may have gone some way to solving the problem. The common problem is that perovskites degrade quickly when exposed to light or to moisture, but when the new cells were tested, they showed good levels of stability.
With the results of the testing, the scientists are now confident that the perovskite cells that they are working on could outperform commercial technology currently being used. However, the team still wants to tweak the technology and to optimise the composition of the materials.
The all-perovskite tandem cells we have demonstrated clearly outline a roadmap for thin-film solar cells to deliver over 30% efficiency, added Oxford professor and co-author of the study Henry Snaith. This is just the beginning.
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