Realizing lamellar nanophase separation in a double-cable conjugated polymer via a solvent annealing process

Abstract

Single-component organic solar cells (OSCs) use one conjugated material as a photo-active layer, which can enhance the stability of cells and simplify the fabrication process compared to two-component OSCs. Among single-component conjugated materials, block conjugated polymers can form lamellar structures that are recognized as the ideal structures for OSCs, while it is difficult to tune the nanophase separation in double-cable conjugated polymers. In this work, for the first time, we show that, by rationally designing chemical structures and post treatment, double-cable polymers are also able to form lamellar structures. This was realized by synthesizing a double-cable conjugated polymer containing both a crystalline conjugated backbone and perylene bisimide side units. When the high boiling point solvent dichlorobenzene with slow evaporation speed is used, the polymers have enough time to self-assemble into well-ordered nanostructures. Therefore, the double-cable polymer formed lamellar structures with a lamellar distance of ∼70 Å and a π–π distance of ∼3.5 Å. These ordered structures facilitate the charge transport and result in improved photocurrent and power conversion efficiency compared to other disordered nanostructures.