Non‐Fullerene Acceptor‐Based Nanomorphology Enhancement for Efficient Ternary Organic Solar Cells

Recently, the ternary active‐layer‐based organic solar cells have shown remarkable increment in the power conversion efficiency (PCE) by utilizing the synergistic effect of complementary absorption, band alignment, and nano‐scale morphology enhancement. Non‐fullerene acceptors (NFAs) are an important class of functional materials for the improved performance of ternary organic solar cells due to their role in improvising the light absorption and the morphology of the active layer. Here, the non‐fullerene (NF) molecule, NAI‐FN‐NAI (BO), is used as the third component in the bulk heterojunction of PTB7‐Th: PC71BM to fabricate the ternary organic solar cell. The magical number of the composition, i.e., 20% by weight of the NF in the ternary active layer resulted in the PCE of 8.1% devices, which is almost 35% higher efficiency than PTB7‐Th: PC71BM binary devices having the PCE of 6%. The enhanced efficiency is observed even though the lessened effect of complementary absorption and band alignment factors of the NF. Such an improved efficiency is attributed in ternary devices to the nano‐scale morphology enhancement. It could pave the way to realize the best possible bulk heterojunction blend to attain high PCE close to inorganic counterparts.