A newly designed benzodithiophene building block: tuning of torsional barrier for non-halogenated and non-aromatic solvent-processible photovoltaic polymers
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초록
내용
In this study, a new BDT-based building block, 3-FBDT, was designed and synthesized and incorporated into PBDB-T-2F to yield an eco-friendly (non-aromatic and non-halogenated) solvent-processible photovoltaic copolymer, PBDB-T-2F(3/4). Compared to the building block of PBDB-T-2F, 4-FBDT, an additional alkyl chain was introduced at the 4-position, and the F substituent was moved from the 4- to 3-postion in the thiophene side chain. This chemical modification decreased the HOMO level (with improved VOC) and increased the torsional energy barrier between the thiophene and BDT moieties (with a tilted structure), resulting in a dramatic improvement in the solubility of the resulting polymer, even in non-aromatic/non-halogenated solvents (i.e., THF). Taking advantage of the outstanding processability in THF, PBDB-T-2F(3/4)-based devices maintained high PCEs when the solvent was changed from chloroform to THF.