Low-cost synthesis of small molecule acceptors makes polymer solar cells commercially viable

The acceptor-donor-acceptor (A-D-A) or A-DA'D-A structured small molecule acceptors (SMAs) have triggered substantial progress for polymer solar cells (PSCs). However, the high-cost of the SMAs impedes the commercial viability of such renewable energy, as their synthesis via the classical pyridine-catalyzed Knoevenagel condensation usually suffers from low reaction efficiency and tedious purifying work-up. Herein, we developed a simple and cheap boron trifluoride etherate-catalyzed Knoevenagel condensation for addressing this challenge, and found that the coupling of the aldehyde-terminated D unit and the A-end groups could be quantitatively finished in the presence of acetic anhydride within 15 minutes at room temperature. Compared with the conventional method, the high reaction efficiency of our method is related to the germinal diacetate pathway that is thermodynamically favorable to give the final products. For those high performing SMAs (such as ITIC-4F and Y6), the cost could be reduced by 50% compared with conventional preparation. In addition to the application in PSCs, our synthetic approach provides a facile and low-cost access to a wide range of D-A organic semiconductors for emerging technologies. The high-cost of the acceptor-donor-acceptor structured small molecule acceptors impedes its commercial viability for polymer solar cells. To address this problem, here, the authors developed a simple and cheap boron trifluoride etherate-catalyzed Knoevenagel condensation with high reaction efficiency.

Automated summary

This study developed a simple and inexpensive boron trifluoride etherate-catalyzed Knoevenagel condensation method for the efficient synthesis of high-performing acceptor-donor-acceptor structured small molecule acceptors. Compared with traditional methods, this approach significantly reduces costs and provides an important synthetic tool for the development of PSCs and other emerging technologies.