Charge-carrier dynamics in hybrid metal halide perovskites for next-generation solar cells
<p>Hybrid metal halide perovskites have emerged over the last decade as highly promising materials for use in solar cells. Their advantages include low production costs, and rapidly increasing efficiencies to compete with those of commercially dominant silicon cells. Recently, increasing atten...
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| Format: | Thesis |
| Language: | English |
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2020
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| _version_ | 1826315769184518144 |
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| author | Savill, KJ |
| author2 | Herz, L |
| author_facet | Herz, L Savill, KJ |
| author_sort | Savill, KJ |
| collection | OXFORD |
| description | <p>Hybrid metal halide perovskites have emerged over the last decade as highly promising materials for use in solar cells. Their advantages include low production costs, and rapidly increasing efficiencies to compete with those of commercially dominant silicon cells. Recently, increasing attention has been devoted to the use of perovskites in next-generation photovoltaic devices in order to overcome the efficiency limit for conventional single-junction cells. Work is still needed to identify the most promising perovskite materials for these applications, and to fully understand their relevant properties. This thesis contributes to both goals.</p>
<p>The challenge of identifying the true timescale of charge-carrier cooling in metal halide perovskites, and whether certain compositions in fact show exceptionally slow cooling, is addressed. This is central to assessing the viability of hot-carrier extraction in perovskite solar cells. Key sources of error in previous approaches to determine charge-carrier temperature, which have produced an orders-of-magnitude range of reported cooling times, are identified. An improved model, which accounts for the full photoluminescence lineshape and enables a consistent approach that can be applied to studies across different perovskite compositions, is then described.</p>
<p>Applying this improved model, charge-carrier cooling in FASnI<sub>3</sub> is studied, revealing that observations of a secondary regime of slow charge-carrier cooling are in fact attributable to electronic relaxation, state-filling and recombination in this energetically disordered material. This result highlights that careful analysis of charge-carrier cooling dynamics is vital to assessing the realistic prospects for hot-carrier solar cells. Photoluminescence polarisation memory in FASnI<sub>3</sub> is also examined, finding no persistent polarisation anisotropy within 270 fs. This points to a need for further study to identify the factors that lead such memory to arise from structural changes in certain perovskite compositions.</p>
<p>Finally, the effects of the SnF<sub>2</sub> additive commonly used to improve material quality of tin-containing perovskites are explored for FA<sub>0.83</sub>Cs<sub>0.17</sub>Sn<sub>x</sub>Pb<sub>1-x</sub>I<sub>3</sub> across the lead-tin range. Significant beneficial effects from the suppression of tin oxidation and associated background hole doping, including reduced energetic disorder and increased charge-carrier mobilities and lifetimes, are found with as little as 1 mol% SnF<sub>2</sub> added. The larger amounts of additive that have commonly been used are found to contribute to detrimental non-radiative recombination. These results, unravelling the impacts of SnF<sub>2</sub> on both structural and optoelectronic properties, provide a foundation for control over the properties of mixed tin-lead perovskites for use as low-bandgap absorbers in all-perovskite tandem cells.</p> |
| first_indexed | 2024-03-06T19:15:49Z |
| format | Thesis |
| id | oxford-uuid:185275e9-a109-4ec1-b4d9-7b8ab6717636 |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-12-09T03:32:06Z |
| publishDate | 2020 |
| record_format | dspace |
| spelling | oxford-uuid:185275e9-a109-4ec1-b4d9-7b8ab67176362024-12-01T15:23:41ZCharge-carrier dynamics in hybrid metal halide perovskites for next-generation solar cellsThesishttp://purl.org/coar/resource_type/c_db06uuid:185275e9-a109-4ec1-b4d9-7b8ab6717636condensed matter physicsspectroscopyEnglishHyrax Deposit2020Savill, KJHerz, L<p>Hybrid metal halide perovskites have emerged over the last decade as highly promising materials for use in solar cells. Their advantages include low production costs, and rapidly increasing efficiencies to compete with those of commercially dominant silicon cells. Recently, increasing attention has been devoted to the use of perovskites in next-generation photovoltaic devices in order to overcome the efficiency limit for conventional single-junction cells. Work is still needed to identify the most promising perovskite materials for these applications, and to fully understand their relevant properties. This thesis contributes to both goals.</p> <p>The challenge of identifying the true timescale of charge-carrier cooling in metal halide perovskites, and whether certain compositions in fact show exceptionally slow cooling, is addressed. This is central to assessing the viability of hot-carrier extraction in perovskite solar cells. Key sources of error in previous approaches to determine charge-carrier temperature, which have produced an orders-of-magnitude range of reported cooling times, are identified. An improved model, which accounts for the full photoluminescence lineshape and enables a consistent approach that can be applied to studies across different perovskite compositions, is then described.</p> <p>Applying this improved model, charge-carrier cooling in FASnI<sub>3</sub> is studied, revealing that observations of a secondary regime of slow charge-carrier cooling are in fact attributable to electronic relaxation, state-filling and recombination in this energetically disordered material. This result highlights that careful analysis of charge-carrier cooling dynamics is vital to assessing the realistic prospects for hot-carrier solar cells. Photoluminescence polarisation memory in FASnI<sub>3</sub> is also examined, finding no persistent polarisation anisotropy within 270 fs. This points to a need for further study to identify the factors that lead such memory to arise from structural changes in certain perovskite compositions.</p> <p>Finally, the effects of the SnF<sub>2</sub> additive commonly used to improve material quality of tin-containing perovskites are explored for FA<sub>0.83</sub>Cs<sub>0.17</sub>Sn<sub>x</sub>Pb<sub>1-x</sub>I<sub>3</sub> across the lead-tin range. Significant beneficial effects from the suppression of tin oxidation and associated background hole doping, including reduced energetic disorder and increased charge-carrier mobilities and lifetimes, are found with as little as 1 mol% SnF<sub>2</sub> added. The larger amounts of additive that have commonly been used are found to contribute to detrimental non-radiative recombination. These results, unravelling the impacts of SnF<sub>2</sub> on both structural and optoelectronic properties, provide a foundation for control over the properties of mixed tin-lead perovskites for use as low-bandgap absorbers in all-perovskite tandem cells.</p> |
| spellingShingle | condensed matter physics spectroscopy Savill, KJ Charge-carrier dynamics in hybrid metal halide perovskites for next-generation solar cells |
| title | Charge-carrier dynamics in hybrid metal halide perovskites for next-generation solar cells |
| title_full | Charge-carrier dynamics in hybrid metal halide perovskites for next-generation solar cells |
| title_fullStr | Charge-carrier dynamics in hybrid metal halide perovskites for next-generation solar cells |
| title_full_unstemmed | Charge-carrier dynamics in hybrid metal halide perovskites for next-generation solar cells |
| title_short | Charge-carrier dynamics in hybrid metal halide perovskites for next-generation solar cells |
| title_sort | charge carrier dynamics in hybrid metal halide perovskites for next generation solar cells |
| topic | condensed matter physics spectroscopy |
| work_keys_str_mv | AT savillkj chargecarrierdynamicsinhybridmetalhalideperovskitesfornextgenerationsolarcells |