High-efficiency organic solar cells with solvent-insensitive morphology
Organic solar cells (OSCs) have surpassed 20% power conversion efficiency (PCE) through donor/acceptor material optimization and bulk heterojunction (BHJ) morphology control. However, morphology manipulation via solvent selection, additives, and annealing remains system-specific, causing performance variability and impeding scalability. Wang, Li, Gao and co-workers introduce BTP-TO2, a non-fullerene acceptor bearing an oligo(ethylene glycol) side chain, which enables solvent-insensitive morphology. Devices processed from diverse halogenated and non-halogenated solvents achieve consistent PCEs around 19%. Small-angle neutron scattering (SANS) reveals that in deuterated solutions, PM6:BTP-TO2 blends exhibit a fractal dimension with slope ~ -1 in the intermediate q region (0.005–0.1 Å⁻¹) and ~ -4 in the high q region (0.1–0.3 Å⁻¹), indicating a stable, persistent molecular conformation. The design rules: enhance acceptor side-chain/solvent interaction to maintain stable conformation; weaken polymer donor–NFA intermolecular interactions to promote rod-like donor conformation and preferential precipitation, decoupling film formation dynamics from blend morphology. Devices retain >80% of initial efficiency (T80) for over 1200 h under continuous operation, and large-area modules demonstrate consistent performance, supporting industrial scale-up.