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Organic Solar Cells: Absolute Measurement of Domain Composition and Nanoscale Size Distribution Explains Performance in Solar Cells Print
Tuesday, 22 January 2013 00:00

This front cover represents the morphology and resulting device dynamics in organic solar cell blend films of PTB7 and PC71BM, as revealed by combined resonant x-ray scattering and microscopy done at the Advanced Light Source. Harald Ade and co-workers find that the fullerene molecules (red) are miscible in the polymer (blue) up to 30 wt.%, above which they begin to agglomerate (bottom). This agglomeration is important for the optoelectronic processes within the device, but the agglomerates must be kept to small sizes by the solvent processing additive diiodooctane (DIO). Correlation of this morphology with the spectrally resolved quantum efficiency shows that the yellow excitons created upon photoabsorption must arrive at the agglomerate interface for charge separation to occur. The blue electrons and green holes can then percolate through appropriate molecules in the mixed matrix to the electrodes for harvesting of electrical energy. Article Link (PDF)