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Investigating the Molecular Orientation and Thermal Stability of Spiro‐OMeTAD and its Dopants by Near Edge X‐Ray Absorption Fine Structure
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Kerry Hazeldine ,
Rachel E. Cross ,
Gongxizi Ren ,
Arthur Connell,
Chris Kershaw,
Peter Holliman ,
D. Andrew Evans
Advanced Physics Research
Swansea University Authors:
Arthur Connell, Chris Kershaw, Peter Holliman
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DOI (Published version): 10.1002/apxr.202200045
Abstract
This study describes the utilization of near edge X-ray absorption fine structure (NEXAFS) to investigate the hole transporting material (HTM) 2,2ʹ,7,7ʹ-tetrakis(N,N-di-p-methoxyphenylamine)- 9,9ʹ-spirobifluorene (Spiro-OMeTAD) and its most common dopants, lithium bis-(trifluoromethylsulfonyl) imide...
| Published in: | Advanced Physics Research |
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| ISSN: | 2751-1200 2751-1200 |
| Published: |
Wiley
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| Online Access: |
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| URI: | https://cronfa.swan.ac.uk/Record/cronfa63340 |
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| Abstract: |
This study describes the utilization of near edge X-ray absorption fine structure (NEXAFS) to investigate the hole transporting material (HTM) 2,2ʹ,7,7ʹ-tetrakis(N,N-di-p-methoxyphenylamine)- 9,9ʹ-spirobifluorene (Spiro-OMeTAD) and its most common dopants, lithium bis-(trifluoromethylsulfonyl) imide (LiTFSI), 4-tert-butylpiridine (tBP), and 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ). By changing the angle of the sample with respect to the beam, the orientation of the molecules on the surface can be observed. The data suggest that it is difficult to determine any orientational preference for Spiro-OMeTAD deposited on a surface due to the 3D propeller-like geometry of this molecule. Both doped and undoped samples show thermal stability beyond the glass transition temperature of the molecules. Significant changes to the Spiro-OMeTAD spectra are observed with the addition of the dopants, in particular the C K-edge. Differences are also observed in the valence band spectra when dopants are added. It is also demonstrated how the doping combination of LiFTSI with tBP and, F4-TCNQ act as p-type dopants by altering the position of the HOMO levels. The F4-TCNQ induces a larger change in the HOMO levels when compared to the LiTFSI and tBP. These results are important to increase the understanding of Spiro-OMeTAD and the effect dopants have on this material for next generation solar cells. |
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| Keywords: |
F4-TCNQ, hole transporting materials, LiTFSI-tBP, near edge x-ray absorption fine structures, Spiro-OMeTAD, valence band |
| College: |
Faculty of Science and Engineering |
| Funders: |
The authors acknowledge the European Regional Development Fund (ERDF) and the Welsh European Funding Office (WEFO) for funding the second Solar Photovoltaic Academic Research Consortium (SPARC II) and the EPSRC (EP/M015254/2, EP/P030068/1), which supported this research. The research leading to this result has been supported by the project CALIPSOplus under Grant Agreement 730872 from the EU Framework Programme for Research and Innovation HORIZON 2020. |