Polymer Fluorination

Fluorination of the donor polymer is a widely accepted method to improve the power conversion efficiency of organic solar cells with a fullerene-based electron acceptor. However, non-fullerene acceptors have become common replacements for fullerenes due to their many advantages, and the effect of donor polymer fluorination in these systems is not well-studied.

In a recent paper led by Nicole Bauer in the Journal of Materials Chemistry A, members of the You Group show that fluorination in a non-fullerene system can improve the open-circuit voltage and fill factor, similar to fullerene-based devices, and can also largely improve the short-circuit current of the device.

When the fluorinated FTAZ polymer was paired with the high-performing acceptor ITIC, a 30% increase in current, Jsc, was observed compared to the non-fluorinated HTAZ polymer, leading to a high efficiency of 8.4% for the FTAZ-based device, almost double that of the HTAZ-based device.