Effect of Blend Composition on Bulk Heterojunction Organic Solar Cells: A Review

Abstract

Significant research and development in the field of organic photovoltaics (OPVs) has been undertaken in recent years. Impressive results relating to both device performance and fabrication techniques suggest it will be a promising renewable energy technology for future low‐cost electricity generation. The necessity of the heterojunction in OPV cells, due to the large exciton binding energy, places constraints on the design of the photoactive layer. The blend composition, meaning the concentration of the donor and acceptor material in the film, is crucial in determining many aspects of the bulk heterojunction (BHJ) active layer film. In this article, the influence of the blend composition on the film morphology and device performance is reviewed. The mechanisms determining this relationship is explored for three different active layer designs, binary polymer: fullerene blends, ternary blends, and organic–inorganic blend films. Finally, the perovskite solar cell is discussed, with an emphasis on the different perovskite ion compositions which have thus far been explored.