Dr. STEPHAN ULRICH
Fraunhofer Institute for Surface Engineering and Thin Films IST, DE
Dr. Stephan Ulrich is researcher at the Fraunhofer Institute for Surface Engineering and Thin Films IST in Braunschweig (Germany). He wrote his doctoral thesis at the Institute for Solar Energy Research Hameln / Emmerthal (ISFH) on CdTe thin-film solar cells. Since 2005 he has been working at the Fraunhofer IST in several bilateral and public founded projects, including e. g. development of low-emissivity coatings for architectural glazing, research and development of electrochromic materials, manufacturing of n- and p-type TCOs and development of robust interference based sun-control coatings for automotive applications.
Development of Electrochromic Materials
Electrochromic systems are used to switch the transmittance of light. Common applications include architectural glazing, dimmable rear-view mirrors and automotive sunroofs. A number of binary oxides of transition metals are predominantly known as active materials that change their transmission during intercalation of lithium ions. However, these materials are often harmful to health, e. g. NiO or expensive, RhO4, IrO2. In addition, a number of other criteria should be met: high and reversible intercalation capability for lithium, high light/dark switching range, neutral colour impression in dark and bleached state, switching voltage compatible with the respective electrolyte, room temperature deposition using cost-effective large-area coating processes. As part of the joint project »Smart Windows of the 2nd Generation 'ECWin2.0'«, new electrochromic materials based on mixed oxides were investigated at Fraunhofer IST. Examples of such material developments and their achieved electrochromic properties will be presented. These include modified VTiOx and TiNb2O7, which is known in the battery sector as a novel anode material. For the first time, production of such layer by sputter deposition and suitability as an electrochromic material could be demonstrated.