poster prize for Laura Elisa Valle Rios student at the European Crystallographic Meeting (ECM29)

The poster contribution of Laura Elisa Valle Rios (HZB-Department Crystallography) was awarded the CrystEngComm poster price of the Royal Society of Chemistry at the 29^th European Crystallographic Meeting (ECM29) in Rovinj (Croatia). Laura Elisa, a PhD student in the Marie-Curie Initial Training network KESTCELLS and the HZB Graduate School "Materials for Solar Energy Conversion" (MatSEC).

She presented results on structural properties of Kesterites (Cu₂ZnSnSe₄ - CZTSe) 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.

Laura Elisa Valle Rios synthesized off-stoichiometric CZTSe powder samples by solid state reaction and studied the structural and chemical properties. Here she applied different analytical methods using also the HZB's large scale facilities BESSY II and BER II. Moreover she performed experiments at the Spallation Neutron Source (SNS) in Oakridge (US). With the results she obtained from complementary neutron and synchrotron X-ray diffraction experiments  she 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. Laura Elisa could show correlations between chemical composition of the kesterite type semiconductor and intrinsic point defects and defect concentrations. 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.

Laura Elisa Valle Rios works at the HZB (EM-AKR) as a PhD student in the EU-funded Marie-Curie Initial Training Network KESTCELLS (Training for sustainable low cost PV technologies: development of kesterite based efficient solar cells). She is enrolled at the Freie Universtaet Berlin in the joint graduate school "Materials for Solar Energy Conversion" (MatSEC).