Photoelectrochemical methods hold the promise to unite the functions of solar cells and electrolyzers, thus directly converting sunlight to fuels. The recent wave of excitement triggered in the solar energy community by lead halide perovskites has also generated an interest to employ halide-based semiconductors as photoelectrodes. At the same time, chemical, electrochemical, and photoelectrochemical corrosion remains a major issue that needs to be better understood and circumvented. In the first part of this presentation I will show how in situ spectroelectrochemical measurements can contribute to the better understanding of the optoelectronic properties of halide-based photoelectrodes. I will demonstrate how we established a stability window for electrochemical tests for simple metal halides, all-inorganic and hybrid organic-inorganic perovskites. We demonstrated the chemical, structural, and morphological changes of the films in both reductive and oxidative environments. Finally, we correlated the band energy structure of these materials with the corrosion events. In the second part of my talk, the influence of electrochemical bias on the phase segregation in mixed halide perovskites (e.g., CH3NH3PbBr1.5I1.5) will be discussed. I will show that upon trapping holes at the iodide site, the iodide gradually gets expelled from the mixed halide film, leaving behind reformed CH3NH3PbBr3 domains. The implication of this process in photoelectrochemical and photovoltaic applications will be discussed.

Hybrid organic-inorganic perovskite photoelectrodes: Photocorrosion vs. solar fuel generation

2019 Fall National Meeting

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