Development of intrinsically fullerene-compatible polymers: Strategy for developing high performance organic solar cells using a non-halogenated solvent

Because large amounts of solvents are needed for large-scale fabrication of organic solar cells, it is important to develop solar cell processes using environmentally friendly solvents. In the research, we introduce a new approach to control the morphology of polymer:PC₇₁BM blend films by an additive-free and non-halogenated solvent system. Incorporation of a fullerene-compatible o-dichlorobenzene group as the side chain of polythienothiophene-co-benzodithiophene derivatives importantly enhances the compatibility of the polymer with PC₇₁BM and improves the nano-scale morphology of the blend film processed from o-xylene. We studied the effect of introducing the o-dichlorobenzene group onto the polymer on the morphology, charge mobility, and solar cell performances as comparing the cases of the polymer before modification. The developed polymer:PC₇₁BM-based solar cells prepared using o-xylene show a remarkably improved performance with a PCE of 6.07%.