Synthesis of Trifluoromethylated Quinoxaline‐Based Polymers for Photovoltaic Applications

Abstract

Abstract A series of quinoxaline‐based conjugated polymers, in which the electron‐donating benzodithiophene (BDT) unit is linked to the electron‐accepting 6,7‐difluorinated quinoxaline (DFQ) derivatives by a thiophene bridge, is synthesized. To investigate their effects on the intrinsic properties of polymers, strong electron‐withdrawing trifluoromethyl (CF 3 ) groups were incorporated into the meta‐position of the phenyl ring at the 2,3‐positions of the DFQ unit of the reference polymer, labelled PEhB‐FQx, to yield the target polymer PEhB‐FQxCF3. In addition, the 2‐ethylhexyloxy substituents on the BDT donor in PEhB‐FQxCF3 are changed to the more planar 2‐ethylhexyl thiophene units to produce another target polymer PThB‐FQxCF3. Owing to the significant contributions of the CF 3 moiety, PEhB‐FQxCF3 exhibits quite discernible optical and electrochemical properties along with significant enhancement in photovoltaic performances compared to the reference polymer PEhB‐FQx. Furthermore, the incorporation of the alkylthienyl side chains on the BDT moiety confers on the resultant PThB‐FQxCF3 to possess the maximum power conversion efficiency of 7.26% with an open circuit voltage of 0.88 V, short‐circuit current density of 12.20 mA cm −2 , and fill factor of 67.80%.