| 초록 |
We synthesized PTB7 polymers under microwave conditions (M-PTB7, 32k and 75k)) and thermal conditions (T-PTB7, 31k) through Stille-coupling polymerization. In a short time, the microwave-assisted method is robust to raise the Mn of PTB7 without increasing D. On the other hand, M-PTB7(32k) exhibited a lower PCE compared with that of T-PTB7(31k). Interestingly, the higher molecular weight of M-PTB7 led a significant decrease in the device performance (PCE of 2.8%). Because it generates more structural defects from homo-coupling side reactions. It accelerated the formation of homo-coupled units that act as charge trapping sites in PSCs comprising a blend of M-PTB7 and fullerenes (PC70BM), which resulted in a decrease in JSC and FF values. It was explained by several optical spectroscopy methods and the model reaction study. These findings enlighten the importance of controlling the generation of homo-coupled units during the synthesis of PTB7 polymers for high-performance PSCs. |
