Liu, Yuhan;
(2024)
An investigation into the structure and functional properties of vacancy-ordered Tellurium halide perovskites.
Doctoral thesis (Ph.D), UCL (University College London).
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Abstract
This thesis focuses on the synthesis and characterisation of tellurium perovskites A2TeX6 (A = Cs, MA; X = Cl, Br, I). The bandgap tunability of A2TeX6 is verified using powder samples, while the crystal structures of tellurium perovskites are detailed analysed using SXRD, PXRD and NPD. Investigation into the MA2TeX6 lattice shows how the MA dynamics, consequently the crystal structure is affected by temperature. A new method of describing the crystal distortion was discovered when this work evolved to include other A2BX6 perovskites. In addition, the room temperature phase transitions of MA2Te(Cl1-xBrx)6 series reveal how the octahedra affect the perovskite structure. A preferred–oriented thin film deposition is developed by aerosol–assisted deposition at low temperature. As–synthesized A2TeI6 films are applied in electrochemical cells to understand their redox reactions using XPS. In contrast to MA2TeI6, Cs2TeI6 film surface is shielded from further corrosion by the production of CsPF6 in the first cycle. The final part of this thesis is dedicated to investigating the degradation of tellurium perovskites during XPS measurements. X–rays can effectively reduce Te4+ to Te0 and as a result, halogen loss is observed. Incorporating the ion gun and flood gun may encourage the dissociation of volatile components, hence accelerate the radiolysis. Overall chloride perovskites are the most sensitive whereas iodides are the most stable; hybrid perovskites experience greater damage than inorganic perovskites.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | An investigation into the structure and functional properties of vacancy-ordered Tellurium halide perovskites |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Copyright © The Author 2023. Original content in this thesis is licensed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) Licence (https://creativecommons.org/licenses/by-nc/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request. |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Chemical Engineering |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10187297 |
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