Improving Device Efficiency of Polymer/Fullerene Bulk Heterojunction Solar Cells Through Enhanced Crystallinity and Reduced Grain Boundaries Induced by Solvent Additives

The power conversion efficiency of a device incorporating a crystalline polymer/fullerene thin film improves from 5% to 7.3% - a relative increase of 45% - when an additive, diiodohexane (DIH), is present during processing. The DIH-processed active layer exhibits substantially enhanced polymer crystallinity and smaller fractal-like fullerene clusters.