Enhanced Interfacial Electron Transport in Organic Photovoltaics Enabled by Porphyrin Aggregates

Maria Vasilopoulou^a, Ermioni Polydorou^a, Antonios Douvas^a, Panagiotis Argitis^a, Vasilis Papamakarios^a, Athanasios Coutsolelos^b, Stella Kennou^c, Leonidas Palilis^d

^aNational Center for Scientific Research Demokritos, Terma Patriarchou Grigoriou, Athens, 15354, Greece

^bChemistry Department College of Sciences - University of Crete, Voutes Campus 710 03- Heraklion, Crete, Greece

^cDepartment of Chemical Engineering, University of Patras, 26500 Patras, Greece

^dUniversity of Patras, Department of Physics, 26500 Patras, Greece

International Conference on Hybrid and Organic Photovoltaics
Proceedings of International Conference on Hybrid and Organic Photovoltaics 2015 (HOPV15)

Roma, Italy, 2015 May 11th - 13th

Organizer: Filippo De Angelis

Poster, Leonidas Palilis, 038
Publication date: 5th February 2015

The self-assembled aggregation, inherent to many planar molecules, may be used to improve the sensitivity of various fundamental processes by taking advantage of the orientation of molecules within films and at interfaces.Such processes include energy levels alteration, charge and exciton transport, all of which are critical to organic optoelectronics operation. On the other hand, to improve their efficiencies beyond the state-of-the-art organic optoelectronic devices require the energetic losses at the interfaces of organic materials with metal contacts to be minimized. Herein we report on enhanced organic solar cell performance through the incorporation of cathode interfacial layers consisting of self-organized porphyrin nanostructures with a face-on configuration. In particular, a water/methanol-soluble porphyrin molecule, the free base meso-tetrakis(1-methylpyridinium-4-yl)porphyrin chloride, is employed as a novel cathode interlayer in bulk heterojunction organic photovoltaics. It is demonstrated that the self-organization of this porphyrin compound into aggregates in which molecules adopt a face-to-face orientation parallel to the organic semiconducting substrate induces a large local interfacial electric field that results in a significant enhancement of exciton dissociation. Consequently, enhanced photocurrent and open circuit voltage were obtained resulting in overall device efficiency improvement in organic photovoltaics based on bulk heterojunction mixtures of different polymeric donors and fullerene acceptors, regardless of the specific combination of donor–acceptor employed. To highlight the impact of molecular orientation a second porphyrin compound, the Zn-metallated meso-tetrakis(1-methylpyridinium-4-yl)porphyrin chloride, was also studied and it was found that it forms aggregates with an edge-to-edge molecular configuration inducing a smaller increase in the device performance.

The project “Implementing advanced interfacial engineering strategies for highly efficient hybrid solar cells” is implemented under the "ARISTEIA II" Action of the "OPERATIONAL PROGRAMME EDUCATION AND LIFELONG LEARNING" and is co-funded by the European Social Fund (ESF) and National Resources.

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International Conference on Hybrid and Organic Photovoltaics

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