Poster award for MatSEC PhD student at the MRS Spring Meeting
At the MRS Spring Meeting in San Francisco, Kai Neldner was awarded for his poster contribution.
The poster contribution of Kai Neldner (HZB-Department Crystallography) was awarded a poster price of the Symposium "Thin-Film Compound Semiconductors" at the MRS Spring Meeting in San Francisco. Kai Neldner, a PhD student in the HZB Graduate School "Materials for Solar Energy Conversion" (MatSEC) has presented results on structural properties of Kesterites (Cu2ZnSnS4 - CZTS) in relation to its stoichiometry deviations.
The best performances of Kesterite-based thin film solar cells with converion efficiencies of 12.6% were obtained with an absorber material quite different from the stoichiometric compound Cu2ZnSn(S,Se)4, especially with a Cu-poor/Zn-rich composition. Because the electronic properties of a semiconductor are strongly related to its crystal structure, it is of great interest to study the nature of stoichiometry deviations systematically and to connect issues such as phase existence limits.
Kai Neldner synthesized off-stoichiometric CZTS powder samples by solid state reaction and studied the structural and chemical properties. He applied different analytical methods using also the HZB's large scale facilities BESSY II and BER II. With his obtained results he was able to prove that CZTS can accomodate deviations from stoichiometry without collapse of the kesterite type structure by the formation of certain point defects. Thus the crystal structure of CZTS can self-adapt to Cu-poor/Zn-rich and Cu-rich/Zn-poor compositions without any structural changes except in terms of the cation distribution.
- Successful master's degree in IR thermography on solar facadesWe are delighted to congratulate our student employee Luca Raschke on successfully completing her Master's degree in Renewable Energies at the Hochschule für Technik und Wirtschaft Berlin - and with distinction!
- BESSY II: Phosphorous chains – a 1D material with 1D electronic propertiesFor the first time, a team at BESSY II has succeeded in demonstrating the one-dimensional electronic properties of a material through a highly refined experimental process. The samples consisted of short chains of phosphorus atoms that self-organise at specific angles on a silver substrate. Through sophisticated analysis, the team was able to disentangle the contributions of these differently aligned chains. This revealed that the electronic properties of each chain are indeed one-dimensional. Calculations predict an exciting phase transition to be expected as soon as these chains are more closely packed. While material consisting of individual chains with longer distances is semiconducting, a very dense chain structure would be metallic.
- Did marine life in the palaeocene use a compass?Some ancient marine organisms produced mysterious magnetic particles of unusually large size, which can now be found as fossils in marine sediments. An international team has succeeded in mapping the magnetic domains on one of such ‘giant magnetofossils’ using a sophisticated method at the Diamond X-ray source. Their analysis shows that these particles could have allowed these organisms to sense tiny variations in both the direction and intensity of the Earth’s magnetic field, enabling them to geolocate themselves and navigate across the ocean. The method offers a powerful tool for magnetically testing whether putative biological iron oxide particles in Mars samples have a biogenic origin.