The SERS signature of PbS quantum dot oxidation

Lead chalcogenide quantum dots (QDs) are promising candidates for the use as sunlight absorbers in sensitized solar cells. While conversion efficiencies of QD solar cells have reached potentially commercially interesting values in the order of 10%, the devices are prone to fast oxidative degradation...

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Bibliographic Details
Published inVibrational spectroscopy Vol. 91; pp. 157 - 162
Main Authors Stadelmann, Kathrin, Elizabeth, Amala, Martín Sabanés, Natalia, Domke, Katrin F.
Format Journal Article
LanguageEnglish
Published Amsterdam Elsevier B.V 01.07.2017
Elsevier BV
Subjects
Fingerprints
Lead
Oxidation
PbS quantum dots
Photothermal oxidation
Photovoltaic cells
Quantum dots
Raman spectroscopy
Selectivity
Sensitized solar cell degradation
Solar cells
Spectrum analysis
Studies
Surface-enhanced Raman spectroscopy
Sensitized solar cell degradation
PbS quantum dots
Photothermal oxidation
Surface-enhanced Raman spectroscopy
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Summary:Lead chalcogenide quantum dots (QDs) are promising candidates for the use as sunlight absorbers in sensitized solar cells. While conversion efficiencies of QD solar cells have reached potentially commercially interesting values in the order of 10%, the devices are prone to fast oxidative degradation whose mechanism is not understood in detail yet. Furthermore, O2 and/or H2O present during fabrication has been observed to strongly influence device performance. Analytical tools to monitor the chemical state of QDs in situ and on-line, e.g. during fabrication and operation, are sought for. In this work, we demonstrate that surface-enhanced Raman spectroscopy (SERS) provides the chemical selectivity and high sensitivity required to investigate the oxidation behavior of QDs. We investigate the SER signature of PbS QDs that is commonly employed as sensitizer material in solar cells because of their tunable absorption range and simple and cheap fabrication. We observe SERS fingerprints for a set of three model PbS QD samples with different oxidation degrees. Intact PbS QDs exhibit a strong phonon mode around 196cm−1. With increasing PbS oxidation, a relative band intensity increase can be observed in the 250–380cm−1 region. At strong oxidation levels, additional Pb-(sulf)oxide marker bands appear at 614 and 980cm−1. Based on our results, we suggest to employ PbS-oxidation SER spectral markers as monitoring tools during photovoltaic device fabrication.
ISSN:0924-2031
1873-3697
DOI:10.1016/j.vibspec.2016.08.008