Chiral Viologen-Derived Water-Stable Small Band Gap Lead Halides: Synthesis, Characterization, and Optical Properties

Abstract

Chiral organic−inorganic metal halides (OIMHs) are attractive for their potential applications in chiral optoelectronics and spintronics, such as circular polarized light emitters, detectors, and chiral-induced spin selectivity. Here, we report three pairs of chiral OIMHs with great water stability constructed from chiral viologens. These OIMHs contain either 1D or 0D structures, however, with small band gaps around 2 eV. Circular dichroism (CD) spectroscopy on transparent thin films of two OIMH pairs showed a wide CD response covering most of the visible light range. Although the chiral center is not directly attached to the pyridinium in these chiral viologens, the chirality is still successfully transferred into both the band gap and the exciton absorption ranges. Liquid and solid CD studies of the chiral viologens further indicate that the chiral induction inside these OIMHs is possibly through chiral crystallization. This work demonstrated the design strategy of water-stable, small band gap chiral OIMHs through chiral viologens. These low-dimensional chiral materials may provide an interesting system to investigate chiral induction, and their broad CD response may enable their potential application as circular photodetectors with a wide detection range.

Narrow Bandgap 1D Lead Iodide Perovskite with Aminophenyl Viologen

“…Another good example is the family of viologen-based cations that have been intensively investigated in the last years. Viologen’s versatility and synthetic simplicity in combination with its electron-accepting properties resulted in a series of works, investigating new lead iodide-based hybrids for photovoltaic applications containing viologen unit: methyl viologen; − hydroxyethyl viologen, carboxyethyl viologen, and propyl viologen; phenyl viologen; and isopropyl viologen . The obtained materials demonstrate improved stability, suitable optoelectronic properties and reversible photoconductive behavior to become of practical use in photovoltaic applications.…”