Perovskite solar cells have many desirable properties, as they can achieve a high power conversion efficiency, are inexpensive to produce, and have a high absorption efficiency in sunlight. Additionally, perovskite solar cells or modules may 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% can potentially be achieved.
In 2016, imec presented for the first time a semi-transparent perovskite module, developed in collaboration with Solliance, stacked on top of an interdigitated back-contact (IBC) crystalline silicon solar cell in a four-terminal tandem configuration, thereby achieving an overall power conversion efficiency of 20.2% on an aperture area of 4cm2. Imec now reports a significant improvement of this technology resulting in a record high power conversion efficiency of 23.9% for the module-on-cell stack of this size.
“Two innovations are key to this achievement,” explained 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%. 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. Having matched areas of this size makes the fabrication technology more attractive to the solar cell industry.”