Abstract:
Chiral hybrid perovskites promise advanced chiral optoelectronic applications, relying on their structure-property correlation. A reasonable numbers of chiral hybrid perovskites have been already reported, but amongst them, only a few have higher order (more than 2_1) screw axis that is essential to form helical enantiomorphic space groups. For example, there is no report of double perovskites with helical enantiomorphic chiral structures. Here, we address the issue by synthesizing (R- and S-IdPA)_4AgBiI_8 (IdPA: 1-iodopropyl-2-ammonium) layered 2D hybrid double perovskites. (R- and S-IdPA)_4AgBiI_8 crystallize in the enantiomorphic chiral space group pair P4_12_12 and P4_32_12, with fourth order screw axis. Interestingly, gauche- and anti-conformers of IdPA cations are arranged alternately in the crystals. The two conformers have distinctly different noncovalent interactions with the inorganic layers, inducing structural asymmetry in the inorganic layers. Particularly, the AgI_6 unit get hugely distorted, making effective coordination number for Ag ~ 2. The R- and S-enantiomers show mirror-image like circular dichroism spectra originating from the electronic states of the inorganic sublattice. The films of (R- and S-IdPA)_4AgBiI_8 also show wavelength-tunable third-harmonic generation (THG), and more importantly, circularly polarized THG with dissymmetry factor |gTHG-CD| of up to 0.13.
