Electrochemical characterization of halide perovskites: Stability & doping

As halide perovskite materials have emerged at the forefront of optoelectronics development, there is an ongoing need to understand their underlying physics and control their emergent properties. Electrochemistry shows promise to both access fundamental parameters of perovskites and to enhance their performance through doping. However, halide perovskites pose a significant challenge to solution-based electrochemistry, as both aqueous solutions and organic solvents are often destructive to thin films of these materials. This work provides a perspective of recent approaches to electrochemical measurements and modifications of halide perovskites with a specific focus on stability and doping. We also report the electrochemistry of methylammonium lead iodide (MAPbI 3 ) thin films relevant for solar applications with a solvent toolkit based on hydrofluoroethers. Both oxidation and reduction peaks are revealed from electrochemical characterization exhibiting the characteristic HOMO/LUMO levels and additional features. This electrochemical driving is found to have little impact on the photoluminescence or underlying morphology of the thin films. Finally, electrochemical lithium salt doping with this solvent toolkit enhanced the conductivity of a thin film device by nearly two orders of magnitude, demonstrating the utility of this approach for optoelectronic applications. • Brief review of the electrochemistry of perovskites, emphasizing stability and doping. • Results shown with a hydrofluoroether solvent toolkit, a nondestructive electrolyte. • Hydrofluoroether electrochemistry revealed MAPbI 3 oxidation and reduction peaks. • Photoluminescence and morphology were preserved in hydrofluoroether electrolyte. • Hydrofluoroether electrochemical doping increased conductivity nearly 100-fold.