Second-harmonic generation circular dichroism of chiral organic–inorganic hybrid metal halides: Insights and perspectives

Investigating chirality and elucidating the underlying mechanisms in chiral organic–inorganic hybrid metal halides (HMHs) are essential prerequisites for advancing high-performance chiroptoelectronic applications. While various linear chiroptical spectroscopic techniques have been employed to characterize the chirality of HMHs, they often suffer from low signal-to-noise ratios due to limited chiroptical sensitivity. As a complementary alternative, second-harmonic generation circular dichroism (SHG-CD) spectroscopy has been proposed to significantly boost chiroptical sensitivity. Nonetheless, current research on SHG-CD within chiral HMHs predominantly emphasizes SHG efficiency and the magnitude of SHG-CD signals, with insufficient attention to fundamentals and potential practical applications. Therefore, this review intends to summarize the state-of-the-art advances in SHG-CD spectroscopy of chiral HMHs, especially emphasizing photophysical mechanisms, modulation strategies, and representative applications. Furthermore, we address existing challenges in the field and present an insightful outlook on future prospects for SHG-CD spectroscopy in this rapidly evolving discipline.