Impact of strain relaxation on performance of α-formamidinium lead iodide perovskite solar cells

TLDR

The α‑phase FAPbI₃ has a suitable bandgap for solar cells but requires additional cations for stabilization, as these additives can alter the bandgap and introduce lattice strain that creates charge‑carrier trap sites. Substituting small, equimolar amounts of cesium and methylenediammonium for formamidinium reduced lattice strain and trap densities, boosting open‑circuit voltage and achieving a certified 24.4 % power‑conversion efficiency, with encapsulated devices retaining 90 % of their initial efficiency after 400 h under maximum‑power‑point operation. Kim et al., Science, p.

Abstract

Relieving unwanted strain Although the α-phase of formamidinium lead iodide (FAPbI 3 ) has a suitable bandgap for use in solar cells, it must be stabilized with additional cations. These compositions can adversely affect the bandgap and produce lattice strain that creates trap sites for charge carriers. Kim et al. found that substituting small, equimolar amounts of cesium and methylenediammonium cations for formamidinium reduced the lattice strain and trap densities. The enhancement in open-circuit voltage led to a certified power conversion efficiency of 24.4%, and encapsulated devices retained 90% of their initial efficiency after 400 hours of maximal power point operating conditions. Science , this issue p. 108