2D Iodide-based Double Perovskite Templatedby Oligothiophene Spacer Cation
![Top: Schematic of 2D Ag-Bi-I DP self-assembly driven by the templating influence of AE2T cations. Bottom: Calculated band structure (left) and absorption spectrum (right) of [AE2T]2AgBiI8 DP. Spin-orbit coupling (SOC) is essential to obtain qualitatively correct energy bands (blue lines).](https://imagedelivery.net/qXYabcYg0JPsn0bBVWE4SA/65eddcbc-3792-4ec8-b286-0cb9bb9e95c4/Screenshot_2024-08-13_at_2.51.30_PM.png/raw)
In an effort to identify lead-free 2D hybrid organic-inorganic perovskites (HOIPs), double perovskites (DPs) with mixed-valent dual metals such as Ag and Bi are attractive. Additionally, replacing chloride and bromide anions with iodide represents an important target in these systems, due to associated lower bandgaps. So far iodide 2D DPs have proven inaccessible in bulk form when using traditional spacer cations, due to intrinsic instability or formation of competing non-perovskite phases.
By using a specifically designed bifunctionalized oligothiophene cation, (bis-aminoethyl)bithiophene (AE2T), we have synthesized the first example of a 2D Ag−Bi iodide DP with a direct bandgap of 2 eV, templated by the collective influence of aromatic interactions, hydrogen bonding, bidentate tethering, and the structural rigidity associated with the oligothiophene cation.
Our work highlights new avenues for exploring specifically designed organic cations to stabilize otherwise inaccessible 2D HOIPs, with associated potential applications for optoelectronics.
