Synthesis of D–A low-bandgap polymer-based thieno[3,4-b]pyrazine and benzo[1,2-b:4,5-b′]dithiophene for polymer solar cells
文摘
Three D–A low-bandgap polymer-based benzo[1,2-b:4,5-b′]dithiophene (BDT) and thieno[3,4-b]pyrazine (TP) unit with different substituents were synthesized using Stille coupling. The substituent effects were explored. It is found that attaching the phenyl group at the 2,3-positions of thienopyrazine unit is beneficial to good coplanarity and regularity of molecular packing. Meanwhile, attaching the longer alkoxyl side chain at BDT unit or phenyl group at the 2,3-positions of thienopyrazine unit had the relatively deep HOMO (LUMO) energy levels. The three D–A polymers showed good thermal stability and exhibited broad absorption, low bandgap, and order packing structure. As a result, the highest PCE of 1.50 % was achieved for the polymer P2 with the substituents, including hexyldecyloxyl at the BDT unit and phenyl at the TP unit.