Solvent-Vapor-Annealing-Induced Interfacial Self-Assembly for Simplified One-Step Spraying Organic Solar Cells

An effective self-assembly vertical alignment of interfacial molecules from an active solution plays an important role in controlling the ultrathin thickness of an interfacial layer and reducing the manufacturing costs of organic solar cells (OSCs). Until now, however, due to the complex multistage film-forming process, this facile one-step coating approach does not work for spray-coated OSCs, while other coating techniques such as spin coating, blade coating, or slot-die coating do. In this work, we found that the simplified one-step spraying OSCs can be successfully implemented with the aid of solvent vapor annealing (SVA) for both fullerene- and nonfullerene-based systems, making the one-step spray-coating technique attractive for future manufacturing of photovoltaic modules. The sprayed self-assembly interfacial molecule can be spontaneously delaminated from ternary organic mixtures and vertically deposited underneath the photoactive layer, boosting high charge separation and transport capability comparable to the conventional two-step spraying OSCs. Furthermore, the SVA-assisted one-step spraying process was comprehensively investigated by a series of characterization techniques combining in situ solvent dynamic drying process and X-ray photoelectron spectroscopy, making the causal relationship between spraying process control and device performance more clear. This work shows that the introduction of SVA into one-step spraying can not only maintain high photovoltaic performance but also advance the large-scale OSC industry.