Disentangling Refractive Index Contributions in Transient Absorption Spectroscopy of Two-Dimensional Halide...

Area of Science:

• Materials Science
• Solid State Physics
• Optoelectronics

Background:

• Two-dimensional (2D) halide perovskites offer superior optoelectronic properties and stability for light-based technologies.
• Transient absorption (TA) spectroscopy is crucial for studying excited-state dynamics in these materials.
• High refractive indices can complicate TA spectra interpretation due to reflectivity changes.

Purpose of the Study:

• To disentangle the effects of reflectivity changes from intrinsic optical responses in 2D perovskite TA spectroscopy.
• To validate the applicability of Kramers-Kronig constrained analysis for 2D perovskites.
• To provide a reliable method for analyzing TA data of 2D halide perovskites.

Main Methods:

• Utilized Kramers-Kronig constrained variational analysis.
• Investigated the prototypical Ruddlesden-Popper 2D perovskite, phenylethylammonium lead iodide (PEA2PbI4).
• Analyzed photoinduced changes in the real and imaginary parts of the complex dielectric function.

Main Results:

• Photoinduced changes in the real and imaginary dielectric functions were found to be of comparable magnitude.
• Reflectivity effects were shown to have a negligible impact on TA spectra and kinetics.
• The analysis confirmed the validity of the Kramers-Kronig constrained approach.

Conclusions:

• Reflectivity contributions do not significantly alter TA spectra or kinetics in 2D perovskites.
• This work provides confidence in interpreting TA spectroscopy data for 2D halide perovskites.
• The findings reconcile differing literature views on TA spectroscopy of these materials.