Understanding halide migration in lead halide perovskites is important for developing stable perovskites solar cells. Of particular interest is the 2D metal halide perovskite, R2An-1PbnX3n+1 (R+ = phenylethylammonium (PEA), butylammonium (BA); A+ = methylammonium (MA), cesium (Cs), and formamidium (FA); and X- = Cl, Br, and I) and its tunable layer number (n) within the 2D layered architectures. The tunability achieved through compositional variation of R+:A+ ratio, allows the control of optoelectronic properties such as bandgap, exciton binding energy, and charge carrier recombination lifetime. Although 2D perovskites have shown to suppress halide migration in bulk metal halide perovskite films, the halide ion migration in these low-dimensional perovskite film still prevails as seen from the halide ion segregation and dark recovery in mixed halide (Br:I = 50:50) perovskites films with different layer numbers (n = ∞ - 1). The fraction of halide ion segregation upon light-irradiation, as determined from the difference absorption spectra, decreased from 23.2 % (n = ∞) to &lt; 2.5 % (n = 1) as we decrease the dimensionality of the perovskite. The dependence of excited state behavior of 2D perovskites and halide ion mobility on the layer dimensionality in 2D metal halide perovskites will be discussed.

Photoinduced halide ion segregation in 2D-lead halide perovskites

ACS Fall 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.