Insight into the effects of alkoxy side chain position in nonfullerene electron acceptors on the morphological stability of organic solar cells

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.