How to Apply Raman Spectroscopy for Single Crystals and Thin Films of Organic–Inorganic Lead Halide Perovskite

Abstract

Organic–inorganic lead halide perovskite (OLHP) semiconductors have garnered significant attention for their versatile applications in solar cells, LEDs, photodetectors, and transistors, owing to their remarkable optoelectronic properties and facile solution-based fabrication. Understanding the fundamental physicochemical properties of OLHPs remains challenging due to their soft lattice structures and dynamic structural vibrations with molecular motions. It often results in extraordinary charge transporting and energy transfer, which can be found in many devices. Raman spectroscopy emerges as a vital tool for probing these structural properties due to its high resolution and non-destructive nature. This paper reviews Raman spectral analysis for OLHPs, highlighting the complexities in interpreting low and high-frequency vibrational modes associated with PbX₆ octahedra and organic/molecular cations, respectively. We identify the challenges posed by laser-induced degradation and phase transitions during resonance Raman measurements. Our study proposes improved Raman measurement strategies, emphasizing non-resonance conditions and careful selection of laser wavelengths to mitigate artifacts. These strategies aim to enhance the accuracy of Raman spectra and deepen our understanding of the structural dynamics of OLHPs, which is crucial for advancing their application in next-generation optoelectronic devices.