While perovskites have the potential to achieve high efficiency (the world record for a perovskite cell only is just over 25%), most of the best performing perovskite cells today are tiny – less than an inch wide.
Scaling up makes it more difficult to reach potential efficiency limits. Currently, Willow panels, one meter wide, achieve about 10% efficiency. This is overshadowed by commercial silicon panels of similar sizes, which typically achieve around 20% efficiency.
Olga Malinkiewicz, founder and chief technology officer of Willow, says the company’s goal was to release a solar cell made only from perovskite, and lower yields won’t matter if the technology is cheap enough .
Willow is trying to go where silicon solar panels won’t: on roofs that cannot support the weight of heavy glass panels, or towards more specialized applications, such as solar shades, which the company is currently testing. .
As Willow launches thin-film products for more specialized applications, other companies are hoping to beat, or at least join, silicon at its own UK-based game. Oxford PV integrates perovskites in combined perovskite-silicon cells.
Since silicon absorbs light towards the red end of the visible spectrum, and perovskites can be tuned to absorb different wavelengths, coating a layer of perovskite on the silicon cells allows the combined cells to achieve higher yields than silicon alone.
Oxford PV combination cells are heavy and rigid, like silicon-only cells. But because they are the same size and shape, the new cells can easily fit into panels for roof panels or solar farms.
Chris caseOxford PV’s chief technology officer says the company is focused on reducing the discounted cost of electricity, a measure that takes into account the costs of installing and operating a system. While layering perovskites on silicon increases the cost of manufacturing, he says the discounted cost of the combined cell is expected to drop below silicon over time as these new cells are more efficient. Oxford has set several world efficiency records for this cell type in recent years, most recently reaching 29.5%.
Microquanta semiconductor, a Chinese perovskite company based in Hangzhou, also draws inspiration from silicon solar cells. The company manufactures panels from rigid cells covered with glass and manufactured with perovskites.
The Microquanta pilot plant opened in 2020 and is expected to reach 100 megawatts of capacity by the end of the year, according to Buyi Yan, chief technology officer of the company. The company has installed demonstration panels on several buildings and solar farms across China.
Solve for stability
The stability of perovskites improved from minutes to months over the course of a few years. But most silicon cells installed today have a warranty of around 25 years, a goal that perovskites may not yet 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 efficiently through the material. Researchers worked to improve the shelf life of perovskites, both by developing less responsive perovskite recipes and finding better ways to package them.
Oxford PV, Microquanta and Willow all say they have solved the stability problem, at least well enough to sell their first products.
The estimation of long-term performance of solar cells is usually done by accelerated testing, placing the cells or panels under extremely stressful conditions to simulate years of wear and tear. The most common test series for outdoor silicon cells is a series called IEC 61215.