New Type of Polymerized Small A-D-A Acceptors Constructed by Conjugation Extension in the Branched Direction

The current high-performance polymerized small molecular acceptors (PSMAs) are mainly polymerized through terminal groups of small molecular acceptors (SMAs), which will inevitably damage the preferred stackings of terminal groups and render an inferior photoelectric performance of all -polymer solar cells (all-PSCs). In order to liberate terminal groups for more efficient intermolecular stackings, a new pathway to construct PSMAs is explored by extending molecular conjugation in branched directions, thereby affording two PSMAs of SP-T and SP-TT with thiophene and bithiophene as linkers, respectively. Benefiting from more compact/ordered 2r-2r stackings and superior morphology, the SP-T-based all-PSC exhibits facilitated charge generation/transport and suppressed recombination, thus yielding a greatly improved efficiency of 13.54% compared with 9.76% for the SP-TT-based one. Our work not only develops a new type of PSMA featuring much enhanced molecular packings but also demonstrates its great potential for achieving state-of-the-art all-PSCs through the delicate engineering of linkers.

Automated summary

The current polymerization process of high-performance polymerized small molecular acceptors (PSMAs) through terminal groups of small molecular acceptors (SMAs) damages the preferred stackings of terminal groups and weakens the photoelectric performance of all-polymer solar cells (all-PSCs). To improve intermolecular stackings, a new pathway is explored by extending molecular conjugation in branched directions, resulting in two PSMAs of SP-T and SP-TT. The SP-T-based all-PSC exhibits a significantly improved efficiency of 13.54% compared to the SP-TT-based one with an efficiency of 9.76%, due to more compact/ordered stackings and superior morphology.