Dielectric constant enhancement of non-fullerene acceptors via side-chain modification.

The low dielectric constants of conventional organic semiconductors leads to poor charge carrier photogeneration in homojunction organic solar cells due to large exciton binding energies. Increasing the dielectric constant can potentially enhance the spontaneous exciton dissociation rate at room temperature in homojunction cells, and decrease the charge carrier recombination in heterojunction solar cells comprising blends of electron donors and acceptors. We report that substituting the ubiquitous alkyl solubilizing groups with short glycol chains can give non-fullerene electron acceptors with a static dielectric constant of up to 9.8.