Article: Accurate determination of the index of refraction of polymer blend films by spectroscopic ellipsometry
| Title | Accurate determination of the index of refraction of polymer blend films by spectroscopic ellipsometry | ||||||||||||||||
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| Authors | Ng, A1 Li, CH2 Fung, MK1 Djuriŝić, AB1 Zapien, JA4 Chan, WK2 Cheung, KY3 Wong, WY3 | ||||||||||||||||
| Issue Date | 2010 | ||||||||||||||||
| Publisher | American Chemical Society. The Journal's web site is located at http://pubs.acs.org/journals/jpccck/ | ||||||||||||||||
| Citation | Journal Of Physical Chemistry C, 2010, v. 114 n. 35, p. 15094-15101 [How to Cite?] DOI: http://dx.doi.org/10.1021/jp104398f | ||||||||||||||||
| Abstract | To model the performance of a bulk-heterojunction solar cell, it is necessary to obtain information about the index of refraction of the blend layer, which is typically determined by spectroscopic ellipsometry measurements. The optical functions of poly(3-hexylthiophene)-[6,6]-phenyl C 61-butyric acid methyl ester (P3HT-PCBM) blend films have been extensively studied. However, there is a large variation of the reported optical functions in the literature. Because of this fact, as well as the widespread use of P3HT-PCBM films in organic photovoltaics, we have selected this material system as an example and performed a detailed analysis of spectroscopic ellipsometry data. We illustrate the occurrence of multiple solutions and the importance of a dedicated methodology to reach a satisfactory unique solution. The proposed methodology involves the following steps: (1) multisample analysis; (2) independent thickness and surface characterization; (3) use of the adequate optical description of substrate; (4) thickness estimation from transparent range using Cauchy model; (5) fitting n and k in the entire range with fixed thickness; verify result is physically meaningful; (6) optimization of the parameters to be fitted; (7) repeating steps 5 and 6 with and without EMA layer to account for the surface roughness; (8) finally, and only if no satisfactory fit could be obtained from previous steps, attempts to introduce anisotropy, graded layers, or other nonideal models should follow. © 2010 American Chemical Society. | ||||||||||||||||
| ISSN | 1932-7447 2011 Impact Factor: 4.805 2011 SCImago Journal Rankings: 0.435 | ||||||||||||||||
| DOI | http://dx.doi.org/10.1021/jp104398f | ||||||||||||||||
| ISI Accession Number ID | WOS:000284520100063
Funding Information: This work was supported by the Strategic Research Theme, University Development Fund, and Small Project Grant and Outstanding Young Researcher Award (administrated by The University of Hong Kong) are also acknowledged. W.-Y.W. thanks the Hong Kong Research Grants Council for a GRF Grant (HKBU202607), the Hong Kong Baptist University for a Faculty Research Grant (FRG/06-07/II-63) and the Croucher Foundation for a Croucher Senior Research Fellowship. J.A.Z. thanks support from CityU Strategic Research Grants (7002442). The authors thank the Department of EEE, The University of Hong Kong for the use of spectroscopic ellipsometer, as well as Professor C. Surya and Dr. H. F. Lui from the Department of EIE, Hong Kong Polytechnic University for the use of atomic force microscopy (AFM). The authors would also like to thank Dr. Tom Tiwald from J. A. Woollam company for useful discussions concerning the fitting and help in fitting the optical functions of glass substrate. | ||||||||||||||||
| References | References in Scopus |
| dc.contributor.author | Ng, A | ||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| dc.contributor.author | Li, CH | ||||||||||||||||
| dc.contributor.author | Fung, MK | ||||||||||||||||
| dc.contributor.author | Djuriŝić, AB | ||||||||||||||||
| dc.contributor.author | Zapien, JA | ||||||||||||||||
| dc.contributor.author | Chan, WK | ||||||||||||||||
| dc.contributor.author | Cheung, KY | ||||||||||||||||
| dc.contributor.author | Wong, WY | ||||||||||||||||
| dc.date.accessioned | 2010-10-31T11:22:19Z | ||||||||||||||||
| dc.date.available | 2010-10-31T11:22:19Z | ||||||||||||||||
| dc.date.issued | 2010 | ||||||||||||||||
| dc.description.abstract | To model the performance of a bulk-heterojunction solar cell, it is necessary to obtain information about the index of refraction of the blend layer, which is typically determined by spectroscopic ellipsometry measurements. The optical functions of poly(3-hexylthiophene)-[6,6]-phenyl C 61-butyric acid methyl ester (P3HT-PCBM) blend films have been extensively studied. However, there is a large variation of the reported optical functions in the literature. Because of this fact, as well as the widespread use of P3HT-PCBM films in organic photovoltaics, we have selected this material system as an example and performed a detailed analysis of spectroscopic ellipsometry data. We illustrate the occurrence of multiple solutions and the importance of a dedicated methodology to reach a satisfactory unique solution. The proposed methodology involves the following steps: (1) multisample analysis; (2) independent thickness and surface characterization; (3) use of the adequate optical description of substrate; (4) thickness estimation from transparent range using Cauchy model; (5) fitting n and k in the entire range with fixed thickness; verify result is physically meaningful; (6) optimization of the parameters to be fitted; (7) repeating steps 5 and 6 with and without EMA layer to account for the surface roughness; (8) finally, and only if no satisfactory fit could be obtained from previous steps, attempts to introduce anisotropy, graded layers, or other nonideal models should follow. © 2010 American Chemical Society. | ||||||||||||||||
| dc.description.nature | Link_to_subscribed_fulltext | ||||||||||||||||
| dc.identifier.citation | Journal Of Physical Chemistry C, 2010, v. 114 n. 35, p. 15094-15101 [How to Cite?] DOI: http://dx.doi.org/10.1021/jp104398f | ||||||||||||||||
| dc.identifier.doi | http://dx.doi.org/10.1021/jp104398f | ||||||||||||||||
| dc.identifier.epage | 15101 | ||||||||||||||||
| dc.identifier.hkuros | 182101 | ||||||||||||||||
| dc.identifier.isi | WOS:000284520100063
Funding Information: This work was supported by the Strategic Research Theme, University Development Fund, and Small Project Grant and Outstanding Young Researcher Award (administrated by The University of Hong Kong) are also acknowledged. W.-Y.W. thanks the Hong Kong Research Grants Council for a GRF Grant (HKBU202607), the Hong Kong Baptist University for a Faculty Research Grant (FRG/06-07/II-63) and the Croucher Foundation for a Croucher Senior Research Fellowship. J.A.Z. thanks support from CityU Strategic Research Grants (7002442). The authors thank the Department of EEE, The University of Hong Kong for the use of spectroscopic ellipsometer, as well as Professor C. Surya and Dr. H. F. Lui from the Department of EIE, Hong Kong Polytechnic University for the use of atomic force microscopy (AFM). The authors would also like to thank Dr. Tom Tiwald from J. A. Woollam company for useful discussions concerning the fitting and help in fitting the optical functions of glass substrate. | ||||||||||||||||
| dc.identifier.issn | 1932-7447 2011 Impact Factor: 4.805 2011 SCImago Journal Rankings: 0.435 | ||||||||||||||||
| dc.identifier.issue | 35 | ||||||||||||||||
| dc.identifier.scopus | eid_2-s2.0-79951608073 | ||||||||||||||||
| dc.identifier.spage | 15094 | ||||||||||||||||
| dc.identifier.uri | http://hdl.handle.net/10722/125286 | ||||||||||||||||
| dc.identifier.volume | 114 | ||||||||||||||||
| dc.language | eng | ||||||||||||||||
| dc.publisher | American Chemical Society. The Journal's web site is located at http://pubs.acs.org/journals/jpccck/ | ||||||||||||||||
| dc.publisher.place | United States | ||||||||||||||||
| dc.relation.ispartof | Journal of Physical Chemistry C | ||||||||||||||||
| dc.relation.references | References in Scopus | ||||||||||||||||
| dc.title | Accurate determination of the index of refraction of polymer blend films by spectroscopic ellipsometry | ||||||||||||||||
| dc.type | Article |
- The University of Hong Kong
- City University of Hong Kong
- Hong Kong Baptist University
- Centre for Advanced Luminescence Materials