Structure–property relationships for exciton polarons in organic–inorganic hybrid materials

Abstract

By combining materials chemistry to fine-tune crystallographic features with coherent nonlinear spectroscopy, we systematically explore how organic–inorganic interactions affect polaronic coupling in two-dimensional (2D) hybrid semiconductors. We focus on layered metal halide perovskite derivatives (2D-MHPs) in which the photoexcitations manifest as exciton–polarons—coulombically bound electron–hole pairs dressed by lattice vibrations. To address the current lack of quantitative frameworks for characterizing exciton–lattice coupling, we employ resonant impulsive stimulated Raman scattering (RISRS) and nonlinear spectroscopy to accurately determine the Huang–Rhys parameter, a direct measure of lattice displacement induced by exciton–phonon interactions. Our results reveal a clear correlation between polaronic displacement and octahedral lattice distortion, with stronger polaronic coupling emerging from greater distortion induced by organic cation modification. This establishes a robust design principle for enhancing exciton–lattice interactions through targeted chemical engineering. Furthermore, we demonstrate that these structural modifications enable precise control over absorption lineshapes and significantly improve excitonic quantum coherence. These findings pave the way for the development of advanced optoelectronic devices, coherent light sources, and quantum emission technologies, offering a strategic framework for the rational design of next-generation hybrid semiconductor materials.