Heteroatom conjugated-shoulder side-chains-based non-fullerene acceptors for organic solar cells

In the field of organic solar cells (OSCs), shoulder side-chain engi-neering on Y-series non-fullerene acceptors (NFAs) has been the subject of great interest toward realizing high power conversion efficiencies (PCEs). Here, we report a procedure for post-attaching shoulder side chains on Y-series NFAs. Compared with the tradi-tional procedure of pre-attaching side chains, this method has the advantages of using low-cost raw materials and of being more conve-nient for robustly attaching conjugated side chains. As a proof of concept, this method is successfully extended to the synthesis of oxygen (CY-O) and sulfur (CY-S) substituted alkylphenyl side chains. Interestingly, CY-O exhibits a higher crystallinity and suitable morphology and a better trade-off between charge separation rate and triplet generation processes. As a result, CY-O-based OSCs achieve a high PCE of 17.8% relative to that of CY-S (15.7%). Our re-sults demonstrate that post-side-chain engineering is a convenient and low-cost method to construct high-performance NFAs.