Reproducible synthesis of nanocrystals with tunable properties for sustainable energy solutions

ended

The future of materials chemistry is the ability to tune materials properties to meet the demands of specific applications. Nanocrystals (NC) are promising materials because their properties can be tuned with NC diameter. Further tuning can be achieved with materials like non-stoichiometric Cu2S that have tunable properties by incorporating different elements into their structure. One example is Cu2ZnSnS4 (CZTS), a photoabsorber with a tunable band-gap with changes in Cu:Zn ratio. However, in order to take advantage of tunable properties the copper chalcogenide NCs must be made reproducibly. However, the ability to reproducibly synthesize NCs has not been reached due to three challenges. The first is a lack of understanding of the NC nucleation mechanism which results in batch-to-batch variation in NC size. The second is a lack of understanding of NC growth mechanisms and how those depend on growth conditions. The third is phase segregation and cation disorder which often occurs for complex ternary and quaternary materials (like CZTS) synthesized with multiple metal precursors. Studying NC formation mechanisms using in situ X-ray total scattering from synchrotron sources allows for previously unobtainable insight on structure of NCs from precursor to nuclei to NC. In NANO-TUNE, I will study the nucleation and growth of CuS using in situ X-ray total scattering and target subsequent cation exchange with Zn and Sn to make CZTS. The outcomes of NANO-TUNE will be the ability to make NCs more reproducibly and with a great tunability of materials properties. CZTS NCs will be used as a proof of concept to study other copper chalcogenide materials in the future which have a wide range of uses including batteries and sensors. The supervisor of this work, Prof. Jensen, has extensive expertise on studying the structure of ultra-small particles and in situ beamline X-ray total scattering experiments, making the University of Copenhagen the perfect host for this project.