"Polymer and hybrid nanostructures for applications in organic sollar cells investigated with advanced scattering techniques"

Prof. Dr. Peter Müller-Buschbaum, Technische Universität München, Physik-Department, Lehrstuhl für Funktionelle Materialien, Germany

Organic solar cells are an interesting alternative to conventional silicon based solar cells as the feature new possibilities introduced by using a different class of materials namely polymers. Instead of expensive ultra-high vacuum technologies, fabrication can be done at room temperature, using wet chemical processing, and thereby enabling usage of methods such as roll-to-roll printing. As a consequence, the production of organic solar cells has the potential to become very cheap and easy. Moreover, the use of polymers allows for flexible solar cells and light weight devices, which will be usable in a very different fashion as compared to the immobile silicon solar panels. In addition, the energy payback times of organic solar cells are significantly shorter as compared to the today’s silicon solar cells. However, despite all these significant advantages of organic solar cells, still fundamental knowledge is very limited.
In particular, it is challenging to detect the complex morphologies, which are necessary to have high efficiency organic solar cells. The combination of grazing incidence small and wide angle x-ray scattering (GISAXS and GIWAXS) allows for overcoming these challenges.1-4 The crystalline structure is probed with GIWAXS and the mesoscale structure is determined with GISAXS. Based on selected examples, the impact of different layers in the functional stack build-up of organic solar cells,5,6 in-situ studies during printing7 and in-operando studies of organic solar cells8 are presented.

References
[1] M.A.Ruderer, P.Müller-Buschbaum: Morphology of polymer-based bulk heterojunction films for organic photovoltaics (review); Soft Matter 7, 5482-5493 (2011)
[2] P.Müller-Buschbaum: The active layer morphology of organic solar cells probed with grazing incidence scattering techniques (progress report); Adv. Mater. 26, 7692-7709 (2014)
[3] A.Hexemer, P.Müller-Buschbaum: Advanced grazing incidence techniques for modern soft matter materials analysis (feature article); IUCrJ 2, 106-125 (2015)
[4] P.Müller-Buschbaum: Grazing incidence small angle neutron scattering: Challenges and possibilities; Polymer Journal (invited review) 45, 34-42 (2013)
[5] S.Guo, M.A.Ruderer, M.Rawolle, V.Körstgens, C.Birkenstock, J.Perlich, P.Müller-Buschbaum: Evolution of lateral structures during the functional stack build-up of P3HT:PCBM based bulk heterojunction solar cells; ACS Appl. Mater. Interfaces 5, 8581-8590 (2013)
[6] W.Wang, S.Pröller, M.A.Niedermeier, V.Körstgens, M.Philipp, B.Su, S.Yu, S.V.Roth, P.Müller-Buschbaum: Development of the Morphology during Functional Stack Build-up of P3HT:PCBM Bulk Heterojunction Solar Cells with Inverted Geometry; ACS Appl. Mater. Interfaces 7, 602-610 (2015)
[7] C.M.Palumbiny, F.Liu, T.P.Russell, A.Hexemer, C.Wang, P.Müller-Buschbaum: The crystallization of PEDOT:PSS polymeric electrodes probed in-situ during printing; Adv. Mater. 27, 3391-3397 (2015)
[8] C.J.Schaffer, C.M.Palumbiny, M.A.Niedermeier, C.Jendrzejewski, G.Santoro, S.V.Roth, P.Müller-Buschbaum: A direct evidence of morphological degradation on a nanometer scale in polymer solar cells; Adv. Mater. 25, 6760-6764 (2013)