Efficient, stable silicon tandem cells enabled by anion-engineered wide-bandgap perovskites

TLDR

Tuning the perovskite top‑layer bandgap to ~1.7 eV is essential for tandem silicon cells, but bromine‑rich anion compositions with wide bandgaps are structurally unstable, so cation composition is usually varied. Using phenethylammonium with iodine and thiocyanate stabilizes bromine‑rich perovskite films, enabling a tandem silicon cell to achieve >26 % certified efficiency and a perovskite device to retain 80 % of its >20 % efficiency after 1000 h illumination. Kim et al., Science, this issue p.

Abstract

Engineering perovskites with anions The bandgap of the perovskite top layer in tandem silicon solar cells must be tuned to ∼1.7 electron volts. Usually, the cation composition is varied because the bromine-rich anion compositions with wide bandgaps are structurally unstable. Kim et al. show that by using phenethylammonium as a two-dimensional additive, along with iodine and thiocyanate, bromine-rich perovskite films can be stabilized. A tandem silicon cell delivered >26% certified power conversion efficiency, and a perovskite device maintained 80% of its initial power conversion efficiency of >20% after 1000 hours under illumination. Science , this issue p. 155