Improvement in thermal stability of solar cell using a non-fullerene n-type liquid crystalline semiconductor

A non-fullerene n-type semiconductor material based on a central benzothiadiazole moiety flanked with octyl-vinylimides (4,7-bis(4-(N-octyl-phthalimide)vinyl)benzo[c]1,2,5-thiadiazole, OPIBT) was synthesized. OPIBT was found to be a liquid crystalline material with a smectic phase. We fabricated a solar cell with a bulk heterojunction structure using OPIBT and poly(3-hexylthiophene-2,5-diyl) as a p-type semiconductor. On comparing it with a solar cell using a compound with a similar skeleton but exhibiting no liquid crystallinity, we found the thermal stability of the OPIBT solar cells to be superior.