posted on 2020-03-18, 12:37authored byJunsang Cho, Jeffrey T. DuBose, Prashant V. Kamat
Two-dimensional
(2D) lead halide perovskites with better chemical
stability and tunable dimensionality offer new opportunities to design
optoelectronic devices. We have probed the transient absorption behavior
of 2D lead halide (bromide and iodide) perovskites of different dimensionality,
prepared by varying the ratio of methylammonium:phenylethylammonium
cation. With decreasing dimensionality (n = ∞
→ 1), we observe a blue shift in transient absorption bleach
in agreement with the trend observed with the shift in the excitonic
peak. The lifetime of the charge carriers decreased with decreasing
layer thickness. The dependence of charge carrier lifetime on the
2D layers as well as the halide ion composition shows the dominance
of excitonic binding energy on the charge carrier recombination in
2D perovskites. The excited-state behavior of 2D perovskites discussed
in this study shows the need to modulate the layer dimensionality
to obtain desired optoelectronic properties.