Quinoxaline-based D-A Copolymers Modified through Side Chain and Backbone Modulation to Produce Highly Efficient Polymer Solar Cells
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초록
내용
Quinoxaline (Qx) are widely used as A-units in D-A-type copolymers to control its optical, electrochemical, and photovoltaic properties. First, we adjust the side chain of difluoroquinoxaline with fluoro- or chloro-thiophene to obtain high performance Qx-based D-A-type copolymer. Second, backbone modulation to the D-unit was also carried out by comparing benzodithiophene (BDT) and its expanded π-conjugated plane version of bithienyl-dithieno[2,3-d;2′,3′-d′]benzo[1,2-b:4,5-b′]dithiophene (DTBDT). Larger conjugated planes of DTBDT effectively improve light absorption and charge transport in the resulting polymers, which further enhance the JSC and FF of PSCs. Finally, the influence of chlorine atom on the thiophene side chains in DTBDT was also examined. Through these structural variations, the meaningful structure-property relationship of Qx-based D-A-type polymers can be provided, which is quite useful to develop high performance p-type polymer donors for photovoltaic applications.