Vapor-assisted pre-solvation for stable and solution-processable quantum dot conductive ink

The development of high-performance, stable quantum dot (QD) inks is critical yet challenging for advancing the efficiency and scalability of next-generation solution-processed optoelectronic devices. Inorganic lead iodide ligands passivated lead sulfide QDs (PbS-PbI₂) have been attractive for their superior surface passivation and strong inter-dot coupling. However, the state-of-the-art inks typically require strongly coordinating alkylamine solvents to dissociate and solvate the PbI₂ ligand, yet these solvents can continuously etch the QDs, leading to rapid ink degradation within a few hours. Herein, an amine-vapor pre-solvation strategy is proposed using a facile butylamine (BA) vapor (< 10 min) pretreatment of QDs, enabling stable dispersion of QDs in BA-free solvents (e.g., N-methyl-2-pyrrolidone (NMP) and propylene carbonate). The resulting QD inks remain stable for > 60 days with no variation in QD size, while QD films exhibit reduced trap-related losses. Solar cells processed from 60-day-aged NMP inks retain 90% of their initial power conversion efficiency (12.1%), whereas BA-based inks degrade within hours, reducing their device efficiency from 11% to 0.3% after only 4 h of aging. The shelf-stable NMP ink further enables large-area blade-coating of uniform PbS-PbI₂ films, manifesting the potential in scalable manufacturing of high-performance QD optoelectronic devices.