Efficient Air-Processed Green-Solvent Based Organic Solar Cells Fabricated via Facile Extremely Low-Temperature Induced Crystallization Approach

Glove-Box (GB)-processed organic solar cells (OSCs) using halogenated solvents exhibited ∼20% power conversion efficiencies (PCEs). Air-processed (AP) OSCs, irrespective of halogenated or nonhalogenated solvent, consistently exhibit lower PCEs than GB counterparts. Key challenges in AP-OSCs include nanomorphological control and charge-carrier transport issues. To address these challenges, an extremely low-temperature induced crystallization (ELTC) strategy is devised, precisely modulating the crystallinity and packing motifs of photoactive materials from solution-state to film-state. This strategy results in densely packed molecular ordering consisting of polymer as well as nonfullerene acceptors within the blend film, yielding a tuned nanomorphology, having accelerated interfacial hole-transport rates and heightened charge-carrier transport. Consequently, PCEs exceeding 18% for binary and ∼19% for ternary AP-OSCs are achieved, utilizing a halogen-free solvent system. These findings underscore the importance of the ELTC strategy in manipulating molecular packing motifs with reduced stacking distances in the blend film, thus advancing the fabrication of efficient AP-OSCs.