Alcohol-Soluble Conjugated Polymers Enable Highly Efficient and Stable Organic Solar Cells Through a Main-Chain Modulation Strategy

Alcohol-soluble conjugated polymers have been demonstrated as effective cathode interlayer materials (CIMs) in organic solar cells (OSCs). In addition to device efficiency, stability and material preparation costs are also of critical importance. However, limited studies have focused on the intrinsic stability and synthesis procedures of CIMs. To enhance device efficiency and stability while simplifying the material synthesis process, alcohol-soluble conjugated polymers, PNDITphN and PNDITphN-Br, were synthesized through direct arylation polycondensation with precise modulation of the main-chain structures. Both polymers demonstrated superior power conversion efficiency (PCE) compared with PFN-Br. Notably, devices based on PNDITphN exhibited relatively higher PCE than those based on PNDITphN-Br, attributed to its face-on molecular packing, more uniform surface morphology, and stronger interfacial contact with the active layer. As a result, ternary devices using PNDITphN and PNDITphN-Br achieved maximum PCEs of 18.84% and 18.36%, respectively. Moreover, PNDITphN-based devices enhanced light stability compared to those based on PFN-Br and PNDITF3N. These findings provide new insights into cathode interlayer engineering for achieving highly efficient and stable OSCs.