Investigation of charge-transfer dynamics in organic materials for solar cells
<p>This thesis improves our understanding of the charge-transfer dynamics in organic materials employed in dye-sensitized and nanotube-thiophene solar cells. For the purpose of this work, a femtosecond transient absorption spectroscopy setup was built. Additionally, microsecond transient absor...
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| Format: | Thesis |
| Language: | English |
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2014
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| _version_ | 1797112060985737216 |
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| author | Weisspfennig, CT |
| author2 | Herz, L |
| author_facet | Herz, L Weisspfennig, CT |
| author_sort | Weisspfennig, CT |
| collection | OXFORD |
| description | <p>This thesis improves our understanding of the charge-transfer dynamics in organic materials employed in dye-sensitized and nanotube-thiophene solar cells. For the purpose of this work, a femtosecond transient absorption spectroscopy setup was built. Additionally, microsecond transient absorption spectroscopy was utilised to explore dynamics on a longer time-scale.</p> <p>In the first study, the dependence of dye regeneration and charge collection on the pore- filling fraction (PFF) in solid-state dye-sensitized solar cells (DSSCs) is investigated. It is shown that while complete hole transfer with PFFs as low as ~30% can be achieved, improvements beyond this PFF are assigned to a stepwise increase in the charge-collection efficiency in agreement with percolation theory. It is further predicted that the chargecollection efficiency saturates at a PFF of ~82%.</p> <p>The study is followed by an investigation of three novel hole-transporting materials for DSSCs with slightly varying HOMO levels to systematically explore the possibility of reducing the loss-in-potential and thus improving the device efficiency. It is shown that despite one new HTM showing a 100% hole-transfer yield, all devices based on the new HTMs performed worse than those incorporating spiro-OMeTAD. Furthermore, it is demonstrated that the design of the HTM has an additional impact on the electronic density of states present at the TiO<sub>2</sub> electrode surface, and hence influences not only hole- but also electron-transfer from the sensitizer.</p> <p>Finally, a study on a polymer-single-walled carbon nanotube (SWNT) molecular junction is presented. Results from femtosecond spectroscopic techniques show that the polymer poly(3-hexylthiophene) (P3HT) is able to transfer charges to the SWNT within 430 fs. Addition of excess P3HT polymer leads to long-lived free charges making these materials a viable option for solar cells.</p> |
| first_indexed | 2024-03-07T08:19:06Z |
| format | Thesis |
| id | oxford-uuid:add81bd2-f953-44ed-b977-d3e15ea4c411 |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-07T08:19:06Z |
| publishDate | 2014 |
| record_format | dspace |
| spelling | oxford-uuid:add81bd2-f953-44ed-b977-d3e15ea4c4112024-01-16T15:52:54ZInvestigation of charge-transfer dynamics in organic materials for solar cellsThesishttp://purl.org/coar/resource_type/c_db06uuid:add81bd2-f953-44ed-b977-d3e15ea4c411Laser SpectroscopyCondensed Matter PhysicsEnglishOxford University Research Archive - Valet2014Weisspfennig, CTHerz, L<p>This thesis improves our understanding of the charge-transfer dynamics in organic materials employed in dye-sensitized and nanotube-thiophene solar cells. For the purpose of this work, a femtosecond transient absorption spectroscopy setup was built. Additionally, microsecond transient absorption spectroscopy was utilised to explore dynamics on a longer time-scale.</p> <p>In the first study, the dependence of dye regeneration and charge collection on the pore- filling fraction (PFF) in solid-state dye-sensitized solar cells (DSSCs) is investigated. It is shown that while complete hole transfer with PFFs as low as ~30% can be achieved, improvements beyond this PFF are assigned to a stepwise increase in the charge-collection efficiency in agreement with percolation theory. It is further predicted that the chargecollection efficiency saturates at a PFF of ~82%.</p> <p>The study is followed by an investigation of three novel hole-transporting materials for DSSCs with slightly varying HOMO levels to systematically explore the possibility of reducing the loss-in-potential and thus improving the device efficiency. It is shown that despite one new HTM showing a 100% hole-transfer yield, all devices based on the new HTMs performed worse than those incorporating spiro-OMeTAD. Furthermore, it is demonstrated that the design of the HTM has an additional impact on the electronic density of states present at the TiO<sub>2</sub> electrode surface, and hence influences not only hole- but also electron-transfer from the sensitizer.</p> <p>Finally, a study on a polymer-single-walled carbon nanotube (SWNT) molecular junction is presented. Results from femtosecond spectroscopic techniques show that the polymer poly(3-hexylthiophene) (P3HT) is able to transfer charges to the SWNT within 430 fs. Addition of excess P3HT polymer leads to long-lived free charges making these materials a viable option for solar cells.</p> |
| spellingShingle | Laser Spectroscopy Condensed Matter Physics Weisspfennig, CT Investigation of charge-transfer dynamics in organic materials for solar cells |
| title | Investigation of charge-transfer dynamics in organic materials for solar cells |
| title_full | Investigation of charge-transfer dynamics in organic materials for solar cells |
| title_fullStr | Investigation of charge-transfer dynamics in organic materials for solar cells |
| title_full_unstemmed | Investigation of charge-transfer dynamics in organic materials for solar cells |
| title_short | Investigation of charge-transfer dynamics in organic materials for solar cells |
| title_sort | investigation of charge transfer dynamics in organic materials for solar cells |
| topic | Laser Spectroscopy Condensed Matter Physics |
| work_keys_str_mv | AT weisspfennigct investigationofchargetransferdynamicsinorganicmaterialsforsolarcells |