Non-fused and fused ring non-fullerene acceptors

Organic solar cells (OSCs) have attracted attention due to their lightweight, flexibility and transparency. Recent advances in OSC materials, especially non-fullerene acceptors (NFAs), have led to marked improvements. NFAs are characterized by their tunable structures and broad absorption spectra, which enhance charge separation and overall performance. These developments make NFAs pivotal materials in advancing OSC technologies and they represent a promising alternative. The development of fused-ring acceptors (FRAs) has enabled power conversion efficiencies (PCEs) over 19 % to be achieved. Despite this success, the intricate synthesis processes and low material yields result in high production costs limiting the commercial viability of FRAs in OSCs. Conversely, non-fused-ring acceptors (NFRAs) offer significant advantages, including easier synthesis, higher yields and improved stability, facilitating the production of cost-effective OSCs. NFRA-based OSCs have provided similar PCE values to FRAs (above 19 %). The research published in recent months on FRAs - particularly NFRAs - is covered in this review.