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dc.contributor.advisorWells, Justin
dc.contributor.authorGuglielminotti, Arianna
dc.date.accessioned2019-09-05T14:01:17Z
dc.date.available2019-09-05T14:01:17Z
dc.date.issued2019
dc.identifier.urihttp://hdl.handle.net/11250/2612795
dc.description.abstract
dc.description.abstractIn this work, Photoelectron Spectroscopy (PES) was employed to analyse elemental composition and energy band gap of Cu2ZnSnS4 (CZTS) stabilized nanoink deposited films, with the aim of understanding the behavior and effects of the ligand-nanoparticle (NP) interface. Samples were prepared with 1-dodecanethiol ((S)2-anions), thiostannate complex ((Sn2S6)4- anions) and oleylamine (C-chains) coatings. The results of X-ray photoemission (XPS) analysis were necessary in order to understand the contribution of ligands to the overall signal, and to detect possible secondary phases. XPS conclusion helped to determine the relative size of the ligands with respect to the electron mean free path, as well as the presence of Cu3SnS4 (CTS) phase at the outer surface of the NPs and the existence of consistent sulfoxide compounds in the deposited layer. Ultraviolet photoemission (UPS) and Inverse photoemission (IPES) provided insights to the energy band gap of the different films, showing the insulating behavior of the capping agents. All the samples underwent thermal treatment, in order to understand, by evaporation of the capping agents, the dipole-induced behavior of the presence of ligands at the NP surface. The presence of dipoles due to (S)2- and (Sn2S6)4- ligands is supposed to induce a shift of all NP energy states to higher binding energies. The main challenge encountered when performing PES on the drop-casted samples regarded high charging of the material, even if the substrate consisted of Si-doped wafers. Such response gave more credit to the hypothesis of the insulating effect of the ligands. A high-crystallinity CZTS sample was provided by the DTU Fotonik department, and used as benchmark for the analysis of the valence band (VB) of the material, as well as for the peak energies of CZTS core levels. Resonance photoemission (RPES) was performed over the crystalline sample at the beamline MATline at ASTRID2 synchrotron in Aarhus University. Results of the RPES analysis provided supporting information about the elemental contribution to the VB of the material: the energy states closer to the VB maximum seemed to be associated to Cu and S, as resonance was observed at photon energies crossing the Cu 3p and S 2p absorption edges.
dc.languageeng
dc.publisherNTNU
dc.titleEffect on band gap of ligands-exchange in solution processed CZTS thin films, analyzed through PES study
dc.typeMaster thesis


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