Morphology Control of D‐A‐D and D‐A‐A Type Donor Polymers via Thiophene‐π‐Siloxane Spacer Engineering to Produce Scalable High‐Performance Organic Photovoltaics

ABSTRACT One of the major challenges for the commercial application of high performance organic solar cells (OSCs) is scaling them from small‐area devices to large‐area submodules (LA‐SMs). Here, we report the design and synthesis of two new π‐conjugated spacer‐functionalized donor polymers (SF‐DPs), D‐A‐D‐π‐siloxane (SCl‐SiO) and D‐A‐alkyl‐A (SCl‐6C), which incorporate thiophene‐π‐siloxane and hexyl alkyl spacer units into a benzodithiophene (BDT) and benzodithiophenedione (BDD) backbone. A promising technique for enhancing the charge transport, morphology, and stability of OSC devices is the use of spacers, which are designed polymer donors with specific side‐chain functionalities. By applying this strategy to LA‐SMs (55 cm 2 ) processed via non‐halogenated solvent (o‐xylene) and bar coating, a record PCE of about 15.5% was attained with remarkable operational stability (> 88%) of original PCE during prolonged light soaking and environmental stress tests. Additionally, small‐area devices exhibited outstanding power conversion efficiencies (PCEs) exceeding 18% (PM6: SCl‐SiO (HMw): Y6‐BO) with reduced bimolecular recombination, enhanced charge mobilities, and well defined nanostructures confirmed by AFM, TEM, and GIWAX analyzes. These results indicate that side chain engineering with thiophene‐π siloxane and hexyl alkyl incorporated spacer units, in conjunction with controlled molecular weight, provides a scalable pathway toward production of stable and highly efficient OSC modules. image