• Karunadasa, Hemamala
• Matheu, Roc
• Breidenbach, Aaron
• Leppert, Linn
• Lee, Young
• Wolf, Nathan
• Ke, Feng
• Liu, Zhenxian
• Lin, Yu

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)[Sn2X6], (X = Br- ( 1Br ) or I- ( 1I )) are occupied by dmpz2+ (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 105 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 dmpz2+ 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.

Topics

• density
• perovskite
• impedance spectroscopy