Control of electronic properties of metal halide perovskites through vacuum co-deposition
<p>As perovskite-based photovoltaic devices near commercialisation, it is imperative to develop thin-film deposition techniques that can be applied on an industrial scale. Vapor deposition is a solvent-free fabrication technique that is widely implemented in industry and can be used to fabrica...
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| Awduron Eraill: | |
| Fformat: | Traethawd Ymchwil |
| Iaith: | English |
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2022
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| _version_ | 1826316380769615872 |
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| author | Lohmann, KB |
| author2 | Johnston, M |
| author_facet | Johnston, M Lohmann, KB |
| author_sort | Lohmann, KB |
| collection | OXFORD |
| description | <p>As perovskite-based photovoltaic devices near commercialisation, it is imperative to develop thin-film deposition techniques that can be applied on an industrial scale. Vapor deposition is a solvent-free fabrication technique that is widely implemented in industry and can be used to fabricate metal halide perovskite thin-films. Understanding and controlling grain growth and structure of polycrystalline thin films of metal halide perovskite semiconductors is an important step in improving the performance of solar cells based on these materials, as it allows for the development of thin-film passivation techniques compatible with large-scale manufacturing.</p>
<p>I demonstrate that it is possible to accurately control the crystallite size of CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub> (MAPbI<sub>3</sub>) thin films by adjusting the substrate temperature during vacuum co-deposition of inorganic (PbI<sub>2</sub>) and organic (CH<sub>3</sub>NH<sub>3</sub>I) (MAI) precursors. Films co-deposited onto a cold substrate temperatures (-2 °C) had large, micrometer-sized crystal grains while films that formed on a room temperature (23 °C) substrate produced grains of only 100 nm in average diameter. I was able to isolate the effects of substrate temperature on crystal growth by developing a new method to control sublimation of the organic precursor. Furthermore, I found substrate temperature directly affects the adsorption rate of MAI, which in turn affects crystal formation and solar cell device performance through changes to the conversion rate of PbI<sub>2</sub> to MAPbI<sub>3</sub> and stoichiometry.</p>
<p>Next, the passivating effect of using PbCl<sub>2</sub> as the inorganic precursor for vapor-deposited CH<sub>3</sub>NH<sub>3</sub>PbI3(MAPbI<sub>3</sub>) is demonstrated, as compared to films fabricated using PbI2 as the inorganic precursor, which is the conventional approach. Furthermore, I find the partial substitution of PbI2 for PbCl2 in [CH(NH<sub>2</sub>)<sub>2]0.83</sub>Cs<sub>0.17</sub>PbI<sub>3</sub> films enhances photoluminescence lifetimes from 5.6 ns to over 100 ns, photoluminescence quantum yield by more than an order of magnitude, and charge carrier mobility from 46 cm<sup>2</sup>/Vs to 56 cm<sup>2</sup>/Vs. This approach results in significantly improved solar cell power conversion efficiency, from 16.4% to 19.3% for the devices employing perovskite films deposited with 20% substitution of PbI<sub>2</sub> with PbCl<sub>2</sub>. This method presents a scalable, dry and solvent-free route to passivating non-radiative recombination centres and hence improving the performance of vapor-deposited metal halide solar cells. </p>
<p>This thesis combines an overview of the fundamentals of solar cells and the vapour co-evaporation technique with comprehensive studies of the impact of a range of paramters on the optoelectronic properties of the resulting metal-halide perovskite films, providing detailed understanding of the mechanisms that can be used to improve the performance of vacuum-deposited metal-halide perovskite solar cells.</p> |
| first_indexed | 2024-03-07T07:48:10Z |
| format | Thesis |
| id | oxford-uuid:3c893545-1ec8-4667-b2fc-67a58ec2cf9e |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-12-09T03:44:08Z |
| publishDate | 2022 |
| record_format | dspace |
| spelling | oxford-uuid:3c893545-1ec8-4667-b2fc-67a58ec2cf9e2024-12-07T15:28:48ZControl of electronic properties of metal halide perovskites through vacuum co-depositionThesishttp://purl.org/coar/resource_type/c_db06uuid:3c893545-1ec8-4667-b2fc-67a58ec2cf9eCondensed matterPhysicsEnglishHyrax Deposit2022Lohmann, KBJohnston, MSnaith, H<p>As perovskite-based photovoltaic devices near commercialisation, it is imperative to develop thin-film deposition techniques that can be applied on an industrial scale. Vapor deposition is a solvent-free fabrication technique that is widely implemented in industry and can be used to fabricate metal halide perovskite thin-films. Understanding and controlling grain growth and structure of polycrystalline thin films of metal halide perovskite semiconductors is an important step in improving the performance of solar cells based on these materials, as it allows for the development of thin-film passivation techniques compatible with large-scale manufacturing.</p> <p>I demonstrate that it is possible to accurately control the crystallite size of CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub> (MAPbI<sub>3</sub>) thin films by adjusting the substrate temperature during vacuum co-deposition of inorganic (PbI<sub>2</sub>) and organic (CH<sub>3</sub>NH<sub>3</sub>I) (MAI) precursors. Films co-deposited onto a cold substrate temperatures (-2 °C) had large, micrometer-sized crystal grains while films that formed on a room temperature (23 °C) substrate produced grains of only 100 nm in average diameter. I was able to isolate the effects of substrate temperature on crystal growth by developing a new method to control sublimation of the organic precursor. Furthermore, I found substrate temperature directly affects the adsorption rate of MAI, which in turn affects crystal formation and solar cell device performance through changes to the conversion rate of PbI<sub>2</sub> to MAPbI<sub>3</sub> and stoichiometry.</p> <p>Next, the passivating effect of using PbCl<sub>2</sub> as the inorganic precursor for vapor-deposited CH<sub>3</sub>NH<sub>3</sub>PbI3(MAPbI<sub>3</sub>) is demonstrated, as compared to films fabricated using PbI2 as the inorganic precursor, which is the conventional approach. Furthermore, I find the partial substitution of PbI2 for PbCl2 in [CH(NH<sub>2</sub>)<sub>2]0.83</sub>Cs<sub>0.17</sub>PbI<sub>3</sub> films enhances photoluminescence lifetimes from 5.6 ns to over 100 ns, photoluminescence quantum yield by more than an order of magnitude, and charge carrier mobility from 46 cm<sup>2</sup>/Vs to 56 cm<sup>2</sup>/Vs. This approach results in significantly improved solar cell power conversion efficiency, from 16.4% to 19.3% for the devices employing perovskite films deposited with 20% substitution of PbI<sub>2</sub> with PbCl<sub>2</sub>. This method presents a scalable, dry and solvent-free route to passivating non-radiative recombination centres and hence improving the performance of vapor-deposited metal halide solar cells. </p> <p>This thesis combines an overview of the fundamentals of solar cells and the vapour co-evaporation technique with comprehensive studies of the impact of a range of paramters on the optoelectronic properties of the resulting metal-halide perovskite films, providing detailed understanding of the mechanisms that can be used to improve the performance of vacuum-deposited metal-halide perovskite solar cells.</p> |
| spellingShingle | Condensed matter Physics Lohmann, KB Control of electronic properties of metal halide perovskites through vacuum co-deposition |
| title | Control of electronic properties of metal halide perovskites through vacuum co-deposition |
| title_full | Control of electronic properties of metal halide perovskites through vacuum co-deposition |
| title_fullStr | Control of electronic properties of metal halide perovskites through vacuum co-deposition |
| title_full_unstemmed | Control of electronic properties of metal halide perovskites through vacuum co-deposition |
| title_short | Control of electronic properties of metal halide perovskites through vacuum co-deposition |
| title_sort | control of electronic properties of metal halide perovskites through vacuum co deposition |
| topic | Condensed matter Physics |
| work_keys_str_mv | AT lohmannkb controlofelectronicpropertiesofmetalhalideperovskitesthroughvacuumcodeposition |