Enhancement of the Power Conversion Efficiency of Organic Solar Cells by Surface Patterning of Azobenzene Thin Films

Nanoscale-patterned azobenzene thin films were incorporated in organic solar cells to scatter incident light, thus increasing the optical path length of photons inside the active area. This ultimately led to significant power conversion efficiency (PCE) enhancements in the active layer. Specifically, the azobenzene thin films were patterned with two-dimensional crossed surface relief gratings inscribed via laser interference lithography. The patterned films were then bleached and thermally stabilized by exposure to strong ultraviolet light before being incorporated in P3HT:PC₆₁BM and PTB7:PC₆₁BM solar cells. The fabricated solar cells exhibited a PCE enhancement of 133%, from 1.37 to 3.19%, for P3HT:PC₆₁BM solar cells, and a PCE enhancement of 302%, from 0.53 to 2.13%, for PTB7:PC₆₁BM solar cells.