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DOE OSTI · 1908586

Halogen Redox Shuttle Explains Voltage-Induced Halide Redistribution in Mixed-Halide Perovskite Devices

Xu, Zhaojian·Kerner, Ross A.·Harvey, Steven P.·Zhu, Kai·Berry, Joseph J.·Rand, Barry P.
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Abstract

Voltage-induced halide segregation greatly limits the optoelectronic applications of mixed-halide perovskite devices, but a mechanistic explanation behind this phenomenon remains unclear. In this work, we use electron microscopy and elemental mapping to directly measure the halide redistribution in mixed-halide perovskite solar cells with quasi-ion-impermeable contact layers under different bias polarities to find iodide and bromide accumulation at the cathode and anode, respectively. This is consistent with a mechanism based on preferential iodide oxidation at the anode, leading to unbalanced I$^{+}_{i}$, I$^{-}_{X}$, and Br$^{-}_{X}$ fluxes. Importantly, switching the anode from "inert" Au to "active" Ag prevents segregation because Ag oxidation precludes the oxidation of lattice iodide, which suggests employing redox-active additives as a general strategy to suppress halide segregation. Finally, these results show that halide perovskite devices operate as solid-state electrochemical cells when threshold voltages are exceeded, providing fresh insight to understand the impacts of voltage bias on halide perovskite devices.

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14 SOLAR ENERGY37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRYelectrochemistryhalide peroskiteshalide segregationphase separationvoltage-induced

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Xu, Zhaojian, Kerner, Ross A., Harvey, Steven P., Zhu, Kai, Berry, Joseph J., Rand, Barry P.. 2022-12-14. Halogen Redox Shuttle Explains Voltage-Induced Halide Redistribution in Mixed-Halide Perovskite Devices. https://doi.org/10.1021/acsenergylett.2c02385

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