Effect of side chains on the electronic and photovoltaic properties of diketopyrrolopyrrole-based molecular acceptors

• Synthesis and characterization of diketopyrrolopyrrole-based π-conjugated molecular systems.
• Simple and accessible non-fullerene molecular acceptors.
• Impact of the side chains on the electronic, photovoltaic and charge transport properties.
• Aggregation controlled via side chain engineering.

Four molecular electron acceptors based on a common phthalimide end-capped diketopyrrolopyrrole π-conjugated backbone, solubilized by different alkyl groups, have been synthesized. The influence of the nature and position of the solubilizing alkyl chains attached at the three constitutive blocks has been investigated. Results collected from UV–Vis absorption spectroscopy, cyclic voltammetry, solar cells fabrication and testing as well as atomic force microscopy show that the mode of substitution has negligible effect at the molecular level but strongly affects the material self-assembling properties, charge carrier transport and in turn, devices performances.

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