Charge Reservoirs in an Expanded Halide Perovskite Analog: Enhancing High‐Pressure Conductivity through Redox‐Active Molecules
Roc Matheu, Feng Ke, Aaron Breidenbach, Nathan R. Wolf, Young Lee, Zhenxian Liu, Linn Leppert, Yu Lin, Hemamala I. Karunadasa
Abstract
Abstract As halide perovskites and their derivatives are being developed for numerous optoelectronic applications, controlling their electronic doping remains a fundamental challenge. Herein, we describe a novel strategy of using redox‐active organic molecules as stoichiometric electron acceptors. The cavities in the new expanded perovskite analogs (dmpz)[Sn 2 X 6 ], (X=Br − ( 1Br ) and I − ( 1I )) are occupied by dmpz 2+ ( N , N ′‐dimethylpyrazinium), with the LUMOs lying ca. 1 eV above the valence band maximum (VBM). Compressing the metal‐halide framework drives up the VBM in 1I relative to the dmpz LUMO. The electronic conductivity increases by a factor of 10 5 with pressure, reaching 50(17) S cm −1 at 60 GPa, exceeding the high‐pressure conductivities of most halide perovskites. This conductivity enhancement is attributed to an increased hole density created by dmpz 2+ reduction. This work elevates the role of organic cations in 3D metal‐halides, from templating the structure to serving as charge reservoirs for tuning the carrier concentration.