- https://www.cells.es/ca/actualitat/agenda/esdeveniments-publics-dalba/morphologies-in-organic-photovoltaics-system-dependent-bottlenecks
- Morphologies in organic photovoltaics: system-dependent bottlenecks
- 2015-09-14T12:00:00+02:00
- 2015-09-14T13:00:00+02:00
- Harald Ade, Dept of Physics and Carbon Electronics Laboratory, NCSU, Raleigh
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Sep 14, 2015
de 12:00 a 13:00 (Europe/Madrid / UTC200) - On
- ALBA Maxwell Auditorium
- Nom de contacte
- Eric Pellegrin
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In bulk heterojunction (BHJ) organic photovoltaics (OPVs), electron donating and electron accepting materials form a complex network of discrete and distributed heterointerfaces and charge transport pathways in the photoactive layer where critical photo-physical processes occur. However, we have insufficient knowledge about the structural properties of these interfaces due to their 3-dimensional arrangement and the paucity of techniques to measure local order and purity.
The presentation will review the use of synchrotron radiation based methods that can uniquely measure critical structural parameters, which includes molecular orientation correlations relative to donor/acceptor heterojunctions [1]. Using polarized resonant soft X-ray scattering [2], the degree of molecular orientation, an order parameter that describes face-on (+1) or edge-on orientation (-1) relative to these discrete heterointerfaces, can be determined. By manipulating the degree of molecular orientation through choice of molecular chemistry and processing solvent characteristics, the importance of this structural parameter on the performance of BHJ OPV devices and charge transfer dynamics can be demonstrated. We will furthermore show how compositional variations can be related to polymer crystal size [3] and how mobility and purity can relate to charge extraction and thus in turn to device performance [4,5,6]. A complete description of actual morphologies and theoretical modeling yet to be developed for OPVs will have to take these factors into account. The role of the mixed domains in a 3 phase morphology for charge separation and recombination will be discussed. Devices with efficiencies up to 10.8% will be discussed [7].
