High-Performance, Ambient-Processable Organic Solar Cells Achieved by Single Terpene-Based Entirely Eco-Friendly Process

Conventional processing solvents for organic electronics pose significant health/environmental risks, prompting the search for greener/safer alternatives. Herein, we develop organic solar cells (OSCs), processed from a single terpene solvent, eucalyptol (Eu), with almost no environmental hazards and toxicity. Notably, a record-high power conversion efficiency (PCE) of 15.1% is achieved without any additive, which is particularly significant given the low PCEs (0.1–3.0%) of previous OSCs using a single terpene. First, we design a small-molecule acceptor (MYBO) with optimized side-chains, offering sufficient solubility while maintaining excellent optoelectronic properties. Second, we develop a processing technique which controls the film-formation kinetics to independently tune the aggregation of polymer donor and MYBO. This enables the formation of well-developed MYBO crystallites embedded within interconnected polymer fibrillar structures. And, all the solution processing can be performed in air without using a glove box, thanks to the eco-friendly Eu process. The devices also exhibit excellent air-stability, retaining more than 92% of the initial PCE after 2300 hr in air. This work provides important guidelines for material designs and processing methods to achieve eco-friendly processed, high-performance OSCs.