Mixed 1D/0D Structures of Chiral Hybrid Lead Halides with an <scp>l</scp>-Nicotinium Spacer Exhibit Broadband Photoluminescence and Polarized Emission
Jared D. Fletcher, Jadupati Nag, Ramin Yazdaanpanah, Saugata Sarker, Sachin Kulkarni, Isaiah W. Gilley, Koray Aydın, Venkatraman Gopalan, Mercouri G. Kanatzidis
Abstract
Hybrid lead halide materials have been highly studied for optoelectronics, but their use with chiral organics in chiro-optoelectronics remains limited. Understanding the ability to impart chirality into bulk materials by incorporating a chiral precursor is of great interest due to unique optical properties directly arising from chirality such as circular dichroism, optical rotatory dispersion, and circularly polarized luminescence. Herein, we used protonated l -nicotine (L-n) (nicotinium cations) as a spacer and templated a variety of structures including a series of (L-n) 3 M 4 X 14 (M = Sn, Pb; X = Cl, Br, I) that take space group P 6 3 in which the lead halide regions template two distinct moieties, both a 1D chain motif and a 0D cluster motif. Hydrogen bonding of the L-n and lone pair expression of the metal play a significant role in structural templating. The materials exhibit large band gaps of 2.70, 3.41, and 3.71 eV for X = I, Br, and Cl, respectively. They also exhibit broadband emission with a large Stokes shift, where the emission can come from both the cluster and chain depending on the composition and excitation. Single crystals exhibit linearly polarized light emission with iodide composition, giving a high degree of polarization of 0.61, among the highest reported for 1D hybrid lead halide materials at room temperature. Solution-processed thin films show strong CD responses corresponding to the choice of organic cation, indicating potential for device investigations.