Excited‐State Dynamics in All‐Polymer Blends with Polymerized Small‐Molecule Acceptors

Abstract

Abstract Polymerizing small‐molecular acceptors (SMAs) is a promising route to construct high performance polymer acceptors of all‐polymer solar cells (all‐PSCs). After SMA polymerization, the microstructure of molecular packing is largely modified, which is essential in regulating the excited‐state dynamics during the photon‐to‐current conversion. Nevertheless, the relationship between the molecular packing and excited‐state dynamics in polymerized SMAs (PSMAs) remains poorly understood. Herein, the excited‐state dynamics and molecular packing are investigated in the corresponding PSMA and SMA utilizing a combination of experimental and theoretical methods. This study finds that the charge separation from intra‐moiety delocalized states (i‐DEs) is much faster in blends with PSMAs, but the loosed π–π molecular packing suppresses the excitation conversion from the local excitation (LE) to the i‐DE, leading to additional radiative losses from LEs. Moreover, the increased aggregations of PSMA in the blends decrease donor: acceptor interfaces, which reduces triplet losses from the bimolecular charge recombination. These findings suggest that excited‐state dynamics may be manipulated by the molecular packing in blends with PSMAs to further optimize the performance of all‐PSCs.

Keywords

• charge generation and recombination
• excited‐state dynamics
• polymerized small molecular acceptor
• transient absorption
• Ï€‐Ï€ stacking