Chiral organic-inorganic hybrid perovskites (OIHPs) are typically investigated for find tunable chiroptical responses in the visible range. The typical range of circular dichroism and g-actors for 300-900 nm is upto 10-2, respectively. Further exploitation of chiral OIHPs beyond the narrow visible range of wavelengths is hampered by an insufficient knowledge of the nature of electronic transition (band to band) and structure-property relations. The difficulties with experimental observation and insufficient experimental base for photons with energy less than 1eV also limited exploratory activities for chiroptical effects in the far-infrared part of the spectrum. Here, we show that the observations of strong chiral phonons with ellipticity reaching –9.17 deg. The chiral phonon modes arise from lattice chirality in chiral OIHPs, as revealed by terahertz circular dichroism spectroscopy. Our findings provide pathways for the design of chiral OIHPs and open the door for the utilization of chiroptical effects in the terahertz area essential for sensing and telecommunication.
