Morphological Study of Nanoparticle−Polymer Solar Cells Using High-Angle Annular Dark-Field Electron Tomography
mediaposted on 09.02.2011 by James C. Hindson, Zineb Saghi, Juan-Carlos Hernandez-Garrido, Paul A. Midgley, Neil C. Greenham
Media is any form of research output that is recorded and played. This is most commonly video, but can be audio or 3D representations.
Electron tomography in high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) mode is used to image networks of nanoparticles within polymer−nanoparticle blend photovoltaic devices. Blends of CdSe nanoparticles (∼6.5 nm diameter spheres and ∼33 nm long nanorods) with poly[2-methoxy-5-(3′,7′-dimethyloctyloxy)-1,4-phenylene vinylene] (OC1C10-PPV) are investigated. Blends using spherical particles are found to contain aggregated regions in which well-connected networks of nanoparticles exist, surrounded by lower-density regions with poorer connectivity. As the ratio of nanoparticles to polymer is increased the aggregated regions increase in size, and the connectivity of the particles in the lower-density regions also increases. This has the effect of increasing the overall percentage of the charge-generating interface connected to the electron-collecting electrode, consistent with the trends observed in device performance. Using nanorods instead of spherical particles results in a highly connected network of particles distributed homogeneously through the film. The nanorods are oriented close to parallel to the plane of the film.