Amplification of Circular Dichroism in Chiral Hybrid Organic-Inorganic Perovskites for Enhanced Circularly Polarized Light Detection

Chiral hybrid organic-inorganic perovskites (HOIPs) have gained increasing attention as promising candidates for advanced optoelectronic applications, due to their excellent combination of electrical properties, optical tunability, and chiroptical as well as spin-polarization characteristics. Despite notable advancements in showcasing the potential of chiral HOIPs for circularly polarized light (CPL)-related applications, their performance in distinguishing CPL still falls short compared to organic materials. Moreover, research has primarily focused on a limited number of chiral spacers and on increasing their content to enhance chiroptical activity, leaving the underlying chirality transfer mechanism and the interplay between components in HOIPs largely unexplored.
In this study, we introduce chiral spacers with chlorine substitutions at different positions on the phenyl ring, leading to the formation of chiral perovskites with distinct crystal structures and circular dichroism (CD) characteristics. Additionally, we incorporate a secondary, achiral spacer to investigate how the interaction between components affects chirality. By examining the crystal structure and chirality transfer in these dual-spacer HOIPs, we observe a deviation from the trends exhibited by pure chiral analogues. Notably, introducing a second organic spacer in HOIPs with ortho-substituted chlorine atoms resulted not only in dimensional alterations but also a significant enhancement of their CD. The highest observed absorption dissymmetry factor (g_CD) value of 0.018 was achieved even with the chiral spacer as a minor component. This significant enhancement may be attributed to symmetry reduction and improved binding interactions between the organic and inorganic layers.
To validate the practical relevance of these materials, we fabricated CPL photodetectors. By leveraging the improved chiroptical properties of HOIPs, we successfully demonstrated efficient CPL-distinguishing devices with dissymmetry factors in the photocurrent higher than the g_CD of the HOIPs themselves. Also, these devices exhibited stable operation, a high on/off ratio, and a specific detectivity (D*) of 1.4 × 10¹² Jones.