High‐Efficiency Organic Solar Cells Based on a Low‐Cost Fully Non‐Fused Electron Acceptor

Abstract A series of tetrathiophene‐based fully non‐fused ring acceptors (4T‐1, 4T‐2, 4T‐3, and 4T‐4), which can be paired with the star donor polymer PBDB‐T to fabricate highly efficient organic solar cells are developed. Tailoring the size of lateral chains can tune the solubility and packing mode of acceptor molecules in neat and blend films. It is found that the incorporation of 2‐ethylhexyl chains can effectively change the compatibility with the donor polymer PBDB‐T, and an encouraging power conversion efficiency of 10.15% is accomplished by 4T‐3‐based organic solar cells. It also presents good compatibility with the other polymer donor and an even higher power conversion efficiency (PCE) of 12.04% is achieved based on D18:4T‐3 blend, which is the champion PCE for the fully non‐fused acceptors. Importantly, these inexpensive tetrathiophene fully non‐fused ring acceptors provide cost‐effective photovoltaic performance. The results demonstrate a high photovoltaic performance from synthetically inexpensive materials could be achieved by the rational design of non‐fused ring acceptor molecules.