Composition-Dependent
Light-Induced Dipole Moment
Change in Organometal Halide Perovskites
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Abstract
In
this work we investigate the compositional dependence of electric
dipole moment in AMX<sub>3</sub> (A: organic; M: metal; X: halogen)
perovskite structures using modulation electroabsorption (EA) spectroscopy.
By sampling various device structures, we show that the second harmonic
EA spectra reflect the intrinsic dipolar property of perovskite films
in a layered configuration. A quantitative analysis of the EA spectra
of CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub>, NH<sub>2</sub>CHNH<sub>2</sub>PbI<sub>3</sub>, and CH<sub>3</sub>NH<sub>3</sub>Sn<sub>0.4</sub>Pb<sub>0.6</sub>I<sub>3</sub> is provided to compare the impact of
the organic and metal cations on the photoinduced response of dipole
moment. Based on the EA results, we propose that the A and M cations
could both largely affect the dielectric and dipolar properties of
the perovskite materials, but through different mechanisms, such as
ionic polarization, rotation of molecular dipoles and charge migration.
These processes occur at different time scales and thus result in
a frequency-dependent dipole response
