Optimizing bicontinuous network morphology by precisely regulating alkyl sulfur group side-chain for organic solar cells

Continuous interpenetrating network morphology on the performance of organic solar cells (OSCs) have the effect of ease, how to control the bulk heterojunction (BHJ) the formation of the fiber morphology is of vital importance. In this study, a series of polymers were synthesized by rationally varying the atoms connecting the conjugated backbone and side chains, PBDT-T-SBDD, PBDT-TS-SBDD and PBDT-TDS-SBDD were used to systematically study the effects of sulfur atom on the electron conformation of the molecule, the morphology of the blend film and the properties of the device. We found that the introduction of sulfur atoms can enhance the intermolecular interaction, thus reducing the energy disorder of the blend film. However, excessive introduction of sulfur atoms leads to excessive steric hindrance of side chain of the molecules, resulting in excessive local aggregation. Compared with PBDT-T-SBDD: Y6 and PBDT-TDS-SBDD: Y6-based OSCs, PBDT-TS-SBDD: Y6-based OSCs has both higher photovoltaic performance, reaching a PCE of 11.33 %, due to the well-defined fiber structure which significantly improves the charge transport channel and phase separation of the blend film.