1 research outputs found
Spatial Inhomogeneity of Methylammonium Lead-Mixed Halide Perovskite Examined by Space- and Time-Resolved Microwave Conductivity
Reducing
the spatial inhomogeneity of solution-processed, multicrystalline
methylammonium lead iodide (MAPbI<sub>3</sub>) perovskite is of great
importance for improving its power conversion efficiency, suppressing
point-to-point deviations, and delaying degradation during operation.
Various techniques, such as conducting-mode atomic force microscopy
and photoluminescence mapping, have been applied for this intriguing
class of materials, revealing nonuniform electronic properties on
the nanometer-to-micrometer scale. Here, we designed a new space-
and time-resolved microwave conductivity system that enables mapping
of the transient photoconductivity with resolution greater than ∼45
μm. We examined the effects of the precursor concentration of
MAPbI<sub>3</sub> and the mixing of halides (I<sup>–</sup> and
Br<sup>–</sup>) on the charge carrier dynamics, crystal size,
and inhomogeneity of the films. The optoelectronic inhomogeneity of
MAPbI<sub>3</sub> and MAPbÂ(I<sub>1–<i>x</i></sub>Br<i><sub>x</sub></i>)<sub>3</sub> on the sub-millimeter
and millimeter scales shows a general correlation with their crystallite
sizes, whereas the precursor concentration and halide mixing affect
the inhomogeneity in a different way, providing a basis for uniform
processing of a multicrystalline perovskite film