LAUSR

Abstract The stable morphology of active layers plays important roles in the applications of organic solar cells. Four fused-ring electron acceptors were synthesized by introduction alkoxy side chains on the π-bridge for IDTP-P-O, on the sp3 carbon of central core for IDTP-O-C, both on the two positions for IDTP-O-O, and reference compound (IDTP-P-C). The results indicate that the presence of alkoxy side chains on the sp3 carbon will retain the large negative electrostatic potential (ESP, ≤-22.79 kcal/mol) of oxygen atoms, impact little on the molecular geometry, absorption, and energy level. However, the introduction of alkoxy side chains on the π-bridge will trigger better backbone planarity, red-shifted absorption, higher HOMO energy level and much less negative ESP (≥−4.58 kcal/mol) due to the additional conjugated effect and intramolecular non-bonded S⋯O interaction. The studies of DSC, AFM, TEM and organic solar cells suggest that the introduction of alkoxy side chains on the sp3 carbon of central core will improve the morphological stability.