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Résumé |
Structural and morphological studies at the nanometer scale are extremely important for many naturally occurring as well as newly developed materials. Organic photovoltaics are one such class of materials that are often intentionally or naturally nanostructured for optimisation of performance. Soft x-ray scattering along with absorption techniques near the water window (Carbon, Nitrogen and Oxygen K-edge) offer unique opportunities for such studies because of the richness of fine structures arising from sensitivity to chemical environments [1, 2, 3]. I will present results from polymeric blends and bilayers that exemplify the capabilities of a multi-method approach using complementary soft x-ray characterization techniques namely Resonant soft x-ray scattering/reflectivity (RsoXS/R), Polarized resonant soft x-ray scattering (P-RSoXS) and scanning transmission x-ray microscopy (STXM). Results presented will include data from recent investigations at the SEXTANTS beamline at Synchrotron SOLEIL on evolution of phase separated domains of P3HT:DTCPA polymeric blends with various loading of DTCPA. P3HT [4] is a well-known thiophene derivative while DTCPA is a highly crystalline conducting organic molecule that has both electron accepting and withdrawing moieties [5]. The investigations show that the samples with moderate loadings of DTCPA have domains of <50 nm size and higher efficiencies as compared to other samples. I will also talk about the status and capabilities of HERMES and SEXTANTS beamlines at synchrotron SOLEIL that are capable of such investigations.
References
1. McNeill, C. R., J.Polymer Sci.B 49, 909-919 (2011).
2. Swaraj, S. et al. NanoLett. 10, 2863-2869 (2010).
3. Collins B. A. et al. R. T. Wang, Nature mat., DOI: 10.1038/NMAT3310.
4. P3HT - poly(3-hexylethiophene)(P3HT), DTCPA - 7,9 di(thiophen-2-yl)-8H-cyclopenta[a]acenaphthy-len-8-one)
5. Swathi S. K. et al., Solar Energy Materials & Solar cells 96, 101-107 (2012).
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