While perovskites have the potential to reach them high efficiency (u world record for a single perovskite cell it is just over 25%), most of the best performing perovskite cells today are tiny – less than an inch wide.
Scaling makes it more difficult to reach potential efficiency limits. Now, Saule panels, which are one meter wide, reach about 10% efficiency. This is evidenced by commercial silicon panels of similar dimensions, which typically hit about 20% efficiency.
Olga Malinkiewicz, Saule’s founder and chief technology officer, says the company’s goal was to make a solar cell only perovskite, and lower efficiency doesn’t matter if the technology is economical enough.
Saule tries to go where silicon solar panels won’t be: to roofs that can’t handle the weight of heavy panels embedded in glass, or to more specialized applications, such as solar-powered shutters, that the company is currently testing.
While Saule launches thin film products for more niche applications, other companies are hoping to beat, or at least join, silicon to their game. Based in the UK Oxford PV incorporates perovskites in perovskite-silicon cell combination.
Since silicon absorbs light toward the red end of the visible spectrum, and perovskites can be tuned to absorb different wavelengths, the coating of a layer of perovskite on top of the silicon cells allows the combined cells to reach at higher silicon efficiency only.
Oxford PV combined cells are heavy and rigid, like silicon-only cells. But since they are the same size and shape, new cells can easily insert panels for roof matrices or solar panels.
Chris Case, Oxford PV’s chief technology officer, says the company is focused on reducing the leveled cost of electricity, a metric that factors the installation of a system and the operating costs of living. While the stratification of perovskites above silicon increases the manufacturing cost, he says the cost leveled by the combined cell will have to fall below the silicon over time because these new cells are more efficient. Oxford has set several world records in efficiency for this type of cell in recent years, recently reaching 29.5%.
Semiconductor Microquanta, a Chinese perovskite company based in Hangzhou, also takes some indications from silicon solar cells. The company manufactures panels from rigid, glazed cells that are made of perovskite.
The Microquanta pilot plant will open in 2020, and should reach 100 megawatts of capacity by the end of the year, he says Buyi Yan, the company’s chief technology officer. The company has demonstration panels installed in several buildings and solar farms across China.
Resolution for stability
The stability of perovskites has improved from minutes to months in the span of a few years. But most silicon cells installed today have a warranty of about 25 years, a goal that perovskites may not even be able to achieve.
Perovskites are particularly sensitive to oxygen and moisture, which can interfere with the bonds in the crystal, preventing electrons from moving effectively through the material. Researchers have been working to improve the lives of perovskites, both by developing less reactive perovskite recipes and finding better ways to pack them.
Oxford PV, Microquanta and Saule all say they have solved the stability problem, at least well enough to sell their first products.
Estimating long-term performance in solar cells is usually done by accelerated testing, putting cells or panels in extra-stressful conditions to simulate years of wear. The most common series of tests for silicon outer cells is a series called IEC 61215.