The influence of the microstructure upon the photovoltaic performance of MDMOPPV: PCBM bulk hetero-junction organic solar cells

Martens, Tom; D’Haen, Jan; Munters, Tom; Goris, Ludwig; Beelen, Z.; Manca, Jean; D’Olieslaeger, M.; Vanderzande, Dirk; Schepper, L. De; Andriessen, Ronn

doi:10.1557/proc-725-p7.11

Cited by 10 publications

(7 citation statements)

References 2 publications

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“…[41] Careful transmission electron microscopy (TEM) investigations were carried out on the mixing behavior of a soluble C 60 derivative and an alkoxy-poly(p-phenylenevinylene). [42,43] These samples were prepared by spin-coating with a film thickness of about 150 nm. Homogeneous films were obtained when a mixing ratio of 1:1 was used.…”

Section: Discussionmentioning

confidence: 99%

Conventional Electron Microscopy and Electron Holography of Organic Solar Cells

Simon

Maennig²,

Lichte

2004

Adv Funct Materials

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Organic solar cells are a promising route towards large‐area and low‐price photovoltaic systems. The devices are composed of at least two layers: the hole‐transport layer and the electron‐transport layer. The light absorption can occur in one or both layers. At the interface of the layers the excitons are separated into charge carriers, and every layer deals with one type of carrier. Higher efficiencies of the separation process can be obtained by using a mixed layer containing both materials to obtain a very high interface area. Although the structure of the mixed layers used plays a crucial role for the device performance, until now the morphologies have not been elucidated. In order to correlate physical and optical findings with structure and morphology for the materials in question, electron microscopy experiments were performed on the single components as well as on the layer systems. The conventional electron microscope is a poor phase microscope. As consequence, weak‐phase objects like organic molecules have to be stained or imaged under strong defocus to produce an observable contrast. Artifacts caused by chemical staining and the appearance of Fresnel diffraction using the defocus technique represent the main problems of conventional microscopy. These artifacts can be avoided using electron holography. Holograms of ultrathin sections of thin layers composed of organic dye molecules were recorded. Subsequently, the phase images were reconstructed. In this manner, we succeeded in obtaining high‐contrast electron micrographs without applying staining or defocus. In addition, holograms of crystalline C60 and zinc phthalocyanine were successfully recorded. Holography has been shown to be a useful tool to image beam‐sensitive and weak‐phase objects without artifacts.

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Section: Discussionmentioning

confidence: 99%

Conventional Electron Microscopy and Electron Holography of Organic Solar Cells

Simon

Maennig²,

Lichte

2004

Adv Funct Materials

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“…This was attributed to increased polymer chain interactions which led to better hole conduction by the conjugated polymer. Martens et al (2002) studied not only the effect of casting solvent, but also the casting method (drop-cast versus spin-coated) on phase separation in MDMO-PPV/PCBM layers. They used AFM to look at the surfaces and TEM to examine cross sections of films.…”

Section: Morphology Of Fullerene-conjugated Polymer Active Layersmentioning

confidence: 99%

Organic Solar Cells: An Overview Focusing on Active Layer Morphology

2006

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Solar cells constructed of organic materials are becoming increasingly efficient due to the discovery of the bulk heterojunction concept. This review provides an overview of organic solar cells. Topics covered include: a brief history of organic solar cell development; device construction, definitions, and characteristics; and heterojunction morphology and its relation to device efficiency in conjugated polymer/fullerene systems. The aim of this article is to show that researchers are developing a better understanding of how material structure relates to function and that they are applying this knowledge to build more efficient light-harvesting devices.

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“…However, since TEM enables to look throughout the films, additional information about the exact phase separated domain sizes can be obtained [12] . By using cryo-ultramicrotomy, it was possible to cut thin cross-sections of the film, and so to reveal shape and distribution of the phase separated regions inside the bulk [13] .…”

Section: Surface and Bulk Morphologymentioning

confidence: 99%

Morphology of MDMO-PPV:PCBM bulk heterojunction organic solar cells studied by AFM, KFM, and TEM

Martens

Beelen

D’Haen

et al. 2003

Organic Photovoltaics III

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The microstructure of MDMO-PPV:PCBM blends as used in bulk hetero-junction organic solar cells was studied by Atomic Force Microscopy (AFM) and Kelvin Force Microscopy (KFM) to image the surface morphology and by means of Transmission Electron Microscopy (TEM) to reveal images of the film's interior.By introducing KFM, it was possible to demonstrate that phase separated domains have different local electrical properties than the surrounding matrix. Since blend morphology clearly influences global electrical properties and photovoltaic performance, an attempt to control the morphology by means of casting conditions was undertaken. By using AFM, it has been proven that not only the choice of solvent, but also drying conditions dramatically influence the blend structure. Therefore, the possibility of discovering the blend morphology by AFM, KFM and TEM makes them powerful tools for understanding today's organic photovoltaic performances and for screening new sets of materials.

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The influence of the microstructure upon the photovoltaic performance of MDMOPPV: PCBM bulk hetero-junction organic solar cells

Cited by 10 publications

References 2 publications

Conventional Electron Microscopy and Electron Holography of Organic Solar Cells

Conventional Electron Microscopy and Electron Holography of Organic Solar Cells

Organic Solar Cells: An Overview Focusing on Active Layer Morphology

Morphology of MDMO-PPV:PCBM bulk heterojunction organic solar cells studied by AFM, KFM, and TEM

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