August

Picture of the Month - August 2017

Here you see current insights into the research of the LaMa groups. A collection of the former pictures can be found in the Gallery.

Monitoring hydrogen diffusion in polycrystalline WO₃ using in-situ transmission spectroscopy

The insertion of ions and electrons in tungsten trioxide (WO₃) results in a reversible coloration of the material. Due to these electrochromic properties WO₃ is used in a variety of applications, such as smart windows. However, the coloration behavior and the corresponding transport mechanisms of the involved charge carriers are not completely understood. The figure shows the space- and time-resolved in-situ investigation of the transmission change of a polycrystalline WO₃ thin film during the lateral diffusion of hydrogen in WO₃. The thin film was micro-structured with a transparent polymer (PMMA) film to insert protons electrochemically into the thin film only in a small bar area.  Due to the resulting concentration gradient, the charge carriers are diffusing inside the WO₃ thin film leading to a coloration change. The space-resolved behavior of the transmission change reveals a concentration dependence of the diffusion coefficient of hydrogen in polycrystalline WO₃ thin films.

This picture was submitted by Simon Burkhardt (Prof. Klar's Group).