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.
- Green hydrogen with PEC electrolysers: New insights into transport processesOne method of storing solar energy is to use PEC electrolysers to produce hydrogen. However, scaling up this technology remains challenging. Now, a team at the HZB Institute for Solar Fuels has used 2D fluorescence imaging and particle velocimetry to observe the movement of ions and dissolved gases within the electrolyte during electrolysis. These new insights may prove useful in the development of larger PEC electrolysers.
- New contact material boosts the efficiency of perovskite solar cellsA newly developed material for the electron contact improves the efficiency of single perovskite solar cells and perovskite/silicon tandem solar cells. The new material is based on a carborane molecule. It offers several advantages over the standard material C60, as shown by the study led by Steve Albrecht’s team. The new material has since been patented and is already commercially available.
- BESSY II: New sample environment allows glimpse into thermocatalytic processesA novel measurement cell allows, for the first time, soft and hard X-ray investigations under high pressures of up to 20 bar and temperatures of up to 400°C. This provides new insights into thermocatalytic processes, such as the Fischer-Tropsch synthesis for producing synthetic fuels. The development of the measurement cell is considered a significant achievement within the Care-O-Sene project.