Perovskite stacked solar cell beats silicon efficiency for the first time

August 11, 2017 // By Nick Flaherty
imec's tandem perovskite silicon solar cell has a record efficiency of 23.9%
Imec has boosted the efficiency of its 4cm perovskite/silicon tandem photovoltaic module to a record 23.9 percent, beating silicon for the first time.

imec is the first to achieve a 4 cm2 module-on-cell stack that outperforms the standalone silicon solar cell.

Perovskite solar cells are cheaper to produce and have a high absorption efficiency in sunlight, and can be engineered to result in various optical and electronic properties but struggle with lifetime. Perovskite solar cells or modules can also be used to boost standard silicon (Si) solar technology when engineered to absorb a spectral range that is complementary to the optical range of silicon cells. By stacking the perovskite solar cells or modules on top of Si solar cells, power conversion efficiencies above 30 percent can potentially be achieved, beating the best single junction Si solar cells.

imec showed a semi-transparent perovskite module last year that was developed in collaboration with the Solliance European solar cell alliance. This used a perovskite cell stacked on top of an interdigitated back-contact (IBC) crystalline silicon solar cell in a four-terminal tandem configuration. This achieved an overall power conversion efficiency of 20.2 percent on an aperture area of 4cm2. That design has been improved to reach the record high power conversion efficiency of 23.9 percent for the module-on-cell stack of this size.

“Two innovations are key to this achievement,” said Tom Aernouts, group leader for thin-film photovoltaics at imec and perovskite PV program manager at Solliance. “First, a different perovskite material (CsFAPbIBr) was used, largely improving the stability and conversion efficiency of the 4cm² semi-transparent perovskite module to 15.3 percent. Second, the architecture of the stack was optimized for minimal optical losses by adding an anti-reflection texture on top of the module and a refractive index matching liquid between the perovskite module and the Si solar cell.”

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