Collecting light with artificial moth eyes
Ammonium tungstate/PSS film surface: (a) SEM picture before pyrolysis; (b & c) SEM picture after pyrolysis. © EMPA
Scientists at EMPA in Zürich and University of Basel have developed a photoelectrochemical cell, recreating a moth’s eye to drastically increase its light collecting efficiency. The cell is made of cheap raw materials – iron and tungsten oxide. Analyses at BESSY II have revealed which chemical processes are useful to facilitate the absorption of light.
Empa researchers Florent Boudoire and Artur Braun have implemented a special microstructure on the photoelectrode surface, which gathers sunlight and does not let it out again. The basis for this innovative structure are tiny particles of tungsten oxide. These yellow microspheres are applied to an electrode and then covered with an extremely thin layer of iron oxide. When light falls on the particles it is internally reflected back and forth, till finally all the light is absorbed. All the entire energy in the beam is now available to use for splitting the water molecules.
In principle the newly conceived microstructure functions like the eye of a moth, explains Florent Boudoire. The eyes of these night active creatures need to collect as much light as possible to see in the dark, and also must reflect as little as possible to avoid detection and being eaten by their enemies. The microstructure of their eyes especially adapted to the appropriate wavelength of light. Empa's photocells take advantage of the same effect.
The swiss team did analyze their samples under the x-ray microscope at BESSY II in order to get detailed information about the absorption of light and the chemical processes which enhance it.
Information of EMPA
Publication in Energy&Environmental Sciences
- Key technology for a future without fossil fuelsIn June and July 2025, catalyst researcher Nico Fischer spent some time at HZB. It was his sabbatical, he was relieved of his duties as Director of the Catalysis Institute in Cape Town for several months and was able to focus on research only. His institute is collaborating with HZB on two projects that aim to develop environmentally friendly alternatives using innovative catalyst technologies. The questions were asked by Antonia Rötger, HZB.
- 5000th patient treated with protons for eye tumoursFor more than 25 years, Charité – Universitätsmedizin Berlin and the Helmholtz-Zentrum Berlin (HZB) have been jointly offering proton radiation therapy for eye tumours. The HZB operates a proton accelerator in Berlin-Wannsee for this purpose, while Charité provides medical care for the patients. The 5000th patient was treated at the beginning of August.
- Iridium-free catalysts for acid water electrolysis investigatedHydrogen will play an important role, both as a fuel and as a raw material for industry. However, in order to produce relevant quantities of hydrogen, water electrolysis must become feasible on a multi-gigawatt scale. One bottleneck is the catalysts required, with iridium in particular being an extremely rare element. An international collaboration has therefore investigated iridium-free catalysts for acidic water electrolysis based on the element cobalt. Through investigations with various methods, among them experiments at the LiXEdrom at the BESSY II X-ray source in Berlin, they were able to elucidate processes that take place during water electrolysis in a cobalt-iron-lead oxide material as the anode. The study is published in Nature Energy.