Thermally Stable, Efficient Polymer Solar Cells with Nanoscale Control of the Interpenetrating Network Morphology

By applying the specific fabrication conditions summarized in the Experimental section and post‐production annealing at 150 °C, polymer solar cells with power‐conversion efficiency approaching 5 % are demonstrated. These devices exhibit remarkable thermal stability. We attribute the improved performance to changes in the bulk heterojunction material induced by thermal annealing. The improved nanoscale morphology, the increased crystallinity of the semiconducting polymer, and the improved contact to the electron‐collecting electrode facilitate charge generation, charge transport to, and charge collection at the electrodes, thereby enhancing the device efficiency by lowering the series resistance of the polymer solar cells. Polymer solar cells with power‐conversion efficiency approaching 5 % and remarkable thermal stability are demonstrated after postproduction thermal annealing at 150 °C. The higher efficiency results from thermally induced morphology modification and improved transport across the interface between the bulk heterojunction material and the Al electrode.