Direct patterning of conductive polymer domains for photovoltaic devices

We report a simple approach to control the morphology of polymer/fullerene solar cells based on electron-beam patterning of polymer semiconductors. This process generates conductive nanostructures or microstructures through an in situ cross-linking reaction, where the size, shape, and density of polymer domains are all tunable parameters. Cross-linked polymer structures are resistant to heat and solvents, so they can be incorporated into devices that require thermal annealing or solution-based processing. We demonstrate this method by building "gradient" and nanostructured poly(3-hexylthiophene)/fullerene solar cells. The power-conversion efficiency of these model devices improves with increasing interfacial area. The flexible methodology can be used to study the effects of active layer design on optoelectronic function.