The power conversion efficiency of 27.1 percent, up from 23 percent for a similar design last year, now beats the most efficient standalone silicon solar cell and further careful tweaking of the perovskite material will bring efficiencies over 30% say the researchers.
Perovskite materials are inexpensive to produce, and have a high absorption efficiency for sunlight. Because they can be made semitransparent, perovskite solar cells and modules can also be used on top of silicon solar cells. minimising the thermal losses in the silicon cell and boosting the overall efficiency. Pure perovskite cells have reached efficiencies of 20.9%.
Imec's tandem cell uses a 0.13 cm² spin-coated perovskite cell developed as part of the Solliance cooperation stacked on top of a 4 cm2 industrial interdigitated back-contact (IBC) silicon cell in a 4-terminal configuration, which has a higher annual energy yield than a 2-terminal configuration. Scaling up the tandem device by using a 4 cm2 perovskite module on a 4 cm2 IBC silicon cell produced an overall efficiency of 25.3%, higher than a silicon cell.
Alongside the Solliance partnership of R&D organizations from the Netherlands, Belgium and Germany, Imec is also a partner in EnergyVille with KU Leuven, VITO and UHasselt. “We have been working on this tandem technology for two years now, and the biggest difference with previous versions is in the engineering and processing of the perovskite absorber, tuning its bandgap to optimize the efficiency for tandem configuration with silicon,” said Manoj Jaysankar, doctoral researcher at imec/EnergyVille.
Imec is now looking for industrial partners to commercialise the technology.