o Solar hydrogen technology has just made a quantum leap thanks to the efforts of the Institute for Solar Fuels at the Helmholtz Centre Berlin (HBZ). Researchers there have just developed a new process for making the metal-oxide thin film photoelectrodes that concentrate solar power to split water and produce green hydrogen (H2, overcoming previous technical obstacles.

The problem the team set out to solve was complex. During manufacturing, the high temperatures needed to deposit the metal-oxides onto the surface (to minimise atomic defects and imperfections in the crystalline material) were too high for the conductive-glass substrate underlying the electrode, which would invariably melt. So they developed a novel “flash heating” technique which heats the thin films intermittently with high-powered laser lamps without melting the glass.

"The heat efficiently reduces structural defects, trap states, grain boundaries, and phase impurities, which would become more challenging to mitigate with an increasing number of elements in the metal-oxides. Therefore, new innovative synthesis approaches are essential. We have now demonstrated this on photoelectrodes made of Ta2O5, TiO2, and WO3, which we heated to 850°C without damaging the substrates," details Dr Ronen Gottesman from HBZ in a press release.

Working with a promising photoelectrode material called α-SnWO4, Gottesman’s team found rapid thermal processing improved electronic properties as well as quality and led to a new record performance of 1 mA/cm2 for this material – 25 percent higher than the previous record. The breakthrough not only brings solar H2 technology forward, but the laser deposition method could also be used to manufacture halide perovskites and quantum dots in next-generation photovoltaics.