Illumination Power-Dependent Electroabsorption of Excitons in a CH₃NH₃PbI₃ Perovskite Film

Abstract

Electroabsorption (E-A) spectra of methylammonium lead triiodide (MAPbI3) are found to depend on the power density of the illumination light (IL-D) in both tetragonal and orthorhombic phases when the modulation frequency (M-F) of the applied electric field ( F ) is low. As IL-D increased, the E-A intensity decreased and the shape of the E-A spectra altered from that similar to the second derivative of the exciton absorption band having a Gaussian profile to the one similar to the first derivative, when the M-F of F is low. When the M-F of F is high, E-A spectra were independent of the power density of illumination. Orientational polarization of excitons is considered to be induced by F having a low M-F with strong photoirradiation, following ion migration of MA+ and I– along the applied field direction enhanced by photoirradiation.

Interface- and Temperature-Sensitive Linear Electric Field Effects on Exciton Absorption of CH3NH3PbI3 Perovskite Films

“…Note that these E-A spectra are represented as EA­(2 f ) spectra. It is noted that the M - F - AEF of F A used in the present study, i.e., 1 kHz, is high enough to neglect the illumination power dependence …”

“…It is noted that the M-F-AEF of F A used in the present study, i.e., 1 kHz, is high enough to neglect the illumination power dependence. 20 EA(1f) and EA(2f) spectra were measured at various temperatures in the range of 290−60 K. The results at 290, 220, 120, and 60 K are shown in Figure 2. The remaining results are shown in the Supporting Information (SI), i.e., Figure S1.…”

“…The resulting EA spectra, EA­(2 f ), have gained popularity as a method to study the photophysics of exciton dissociation and charge generation and to determine the effective mass and exciton binding energy of OIHP films. − The Stark effect and the Franz–Keldysh (FK) oscillation have been used to interpret the measured EA­(2 f ) signal. The kinetics of ion migration in the MAPbI 3 film has recently also been studied using EA­(2 f ) measurements to examine how light intensity influences the shape and magnitude of the EA­(2 f ) signals of exciton absorption with M - F - AEF between 40 Hz and 1 kHz . In contrast with the EA­(2 f ) spectra, linear electric field effects on absorption spectra, i.e., EA spectra obtained by monitoring the absorption signal synchronized at the first harmonic of M - F - AEF , EA­(1 f ), have only been explored to a limited extent. , Linear electric field effects on absorption are usually expected for oriented molecular systems or dye molecules aligned on the surface − to give the first-derivative shape of absorption spectra, coming from the linear Stark shift whose magnitude depends on the difference in electric dipole moment between the ground state and the photoexcited state.…”