Highly Distorted Chiral Two-Dimensional Tin Iodide Perovskites for Spin Polarized Charge Transport

Abstract

Incorporating chiral organic molecules into organic/inorganic hybrid 2D metal-halide perovskites results in a novel family of chiral hybrid semiconductors with unique spin-dependent properties. The embedded chiral organic moieties induce a chiroptical response from the inorganic metal–halide sublattice. However, the structural interplay between the chiral organic molecules and the inorganic sublattice, as well as their synergic effect on the resulting electronic band structure need to be explored in a broader material scope. Here we present three new layered tin iodide perovskites templated by chiral (R/S-)­methylbenzylammonium (R/S-MBA), i.e., (R-/S-MBA)2SnI4, and their racemic phase (rac-MBA)2SnI4. These MBA2SnI4 compounds exhibit the largest level of octahedral bond distortion compared to any other reported layered tin iodide perovskite. The incorporation of chiral MBA cations leads to circularly polarized absorption from the inorganic Sn–I sublattice, displaying chiroptical activity in the 300–500 nm wavelength range. The bandgap and chiroptical activity are modulated by alloying Sn with Pb, in the series of (MBA)2Pb1–x Sn x I4. Finally, we show that vertical charge transport through oriented (R-/S-MBA)2SnI4 thin films is highly spin-dependent, arising from a chiral-induced spin selectivity (CISS) effect. We demonstrate a spin-polarization in the current–voltage characteristics as high as 94%. Our work shows the tremendous potential of these chiral hybrid semiconductors for controlling both spin and charge degrees of freedom.

Organic-to-inorganic structural chirality transfer in a 2D hybrid perovskite and impact on Rashba-Dresselhaus spin-orbit coupling

“…These structural insights, coupled with theoretical findings in our work, enable the discovery and design of an emerging class of multifunctional hybrid systems with an amalgam of semiconducting, chiroptical, and spin-dependent properties. Indeed, the combination of chiral induced spin selectivity of chiral organic molecules [56][57][58][59][60][61][62] and an intrinsic RD spin-splitting in the inorganic framework is a hitherto unexplored aspect unique to 2D chiral HOIPs and might have practical implications in future HOIP-based spintronics. Further, the structural chirality transfer and ensuing lowering of symmetry within the inorganic sublattice opens up a gateway to other emergent properties such as nonlinear light-matter interactions and piezo-/ferroelectricity, not just in 2D HOIPs but also in related diverse low-dimensional metal halide hybrids.…”

Synthesis of two-dimensional phenylethylamine tin–lead halide perovskites with bandgap bending behavior

“…The much higher bandgap of the 0% Sn sample should be attributed to the heavier mass of Pb than that of Sn, which agrees with previous studies. 34,36,40,[58][59][60] However, a special peak shi of the Pb-s orbital emerged when the Sn ratio was 0.25. As a result, the valence band maximum (VBM) changed from Pb-s/Br-p to Sn-s/ Br-p, while the conduction band minimum (CBM) remained mainly Pb-p. Appropriately, the dominant position of Sn-p/Br-p was replaced by Pb-p/Br-p for CBM characters, while the VBM kept Sn-s as the main composition when the Sn ratio was 0.75.…”

“…With the B-site anion changing from Sn to Pb, the bandgap shows a bending and Fan's group ascribed this nonlinear process by density functional theory calculations to the antagonistic action between the spin orbital coupling (SOC) effect and structural distortion. 35,36,[38][39][40][41] However, it should be noted that the transformation process of the component from CH 3 NH 3 SnI 3 to CH 3 NH 3 PbI 3 went along with the change in the phases (from P4mm to I4cm at x > 0.5). 41 Additionally, lattice transformation inuenced the band energy transformation.…”

Innovation of Materials, Devices, and Functionalized Interfaces in Organic Spintronics

“…In addition to chiral molecules, chiral 2D OIHPs can be utilized to achieve the CISS effect. [ 59,165 ] Lu et al. introduced a chiral aromatic amine to induce chirality in 2D OIHPs and obtained ( R / S ) methylbenzylammonium‐based iodide ( R / S ‐MBA) 2 PbI 4 (Figure 11i).…”