High-throughput Study of Metal-oxides Photoelectrodes: The Advantage of Lateral Inhomogeneity of PLDFriday (26.06.2020) 11:50 - 12:10 Room 1
A new approach for high-throughput studying of the thickness-structure-process parameters of ternary metal-oxide CuBi2O4 photoelectrodes, fabricated by pulsed laser deposition, will be presented. CuBi2O4 is a p-type semiconductor (Eg = 1.9 eV), that is considered a promising photocathode material for solar water splitting. The lateral inhomogeneity of pulsed laser deposition (PLD), was utilized to deposit large-area (50x50 mm) CuBi2O4 films with a 40 – 240 nm thickness gradient on transparent conductive substrates, creating libraries of thicknesses on a single substrate, Figure 1a. That enabled us to systematically explore the influence of thickness on the films’ structure by examining different processing parameters. Libraries were post-annealed using rapid thermal processing (RTP, heating by high-power lamps), compared with conventional furnace annealing over a temperature range of 400 – 650 °C. High-throughput X-ray diffraction measurements correlated with automated photoelectrochemical mapping of the libraries show the importance of rapid radiative heating in the processing of pure-phase complex oxides, Figure 1b. This approach enabled us to identify a process parameters window to attain a pure-phase of CuBi2O4, dependent on the material’s thickness, and with that, we were able to mitigate two known challenges in the fabrication of CuBi2O4 photoelectrodes. First, the formation of a single-phase, crystalline CuBi2O4 begins at temperatures above ~ 600 °C, which is too high for the transparent conductive glass substrates (typically a fluorine-doped tin oxide, FTO) on which photoelectrodes are typically deposited. Second, in previous reports of CuBi2O4 photoelectrodes, the material always contains phase impurities, such as CuO and Bi2O3 (both photoactive materials), which affects the optoelectronic properties of the photoabsrober film, potentially decreasing its photoelectrocatalytic performance and stability.
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