Concretized structural evolution supported assembly-controlled film- forming kinetics in slot-die coated organic photovoltaics

H Zhang and CY Tian and ZQ Zhang and ML Xie and JQ Zhang and LY Zhu and ZX Wei, NATURE COMMUNICATIONS, 14, 6312 (2023).

DOI: 10.1038/s41467-023-42018-7

Bulk-heterojunction structured small-area organic solar cells are approaching 20% power conversion efficiency, but the blurred film- forming kinetics in the fabrication of large-area devices causes significant PCE loss and restrains the potential of commercialization. Such blurring came from insufficient knowledge of structural evolution during the film-forming process. Here, we concretize the evolution process with structures detailed to the submolecular level by comprehensive investigations of in-situ UV-vis spectroscopy, Atomic Force Microscope, Grazing Incident Wide Angle X-ray Scattering, and molecular dynamic simulation. With such hierarchical structural knowledge, assembly-controlled film-forming kinetics is proposed to explain the whole picture. Such assembly is determined by molecule configuration and can be tuned via external conditions. Understanding this kinetics will contribute to screening large-area device fabrication conditions, and the detailed structural knowledge could inspire the future design of novel photovoltaic materials that are intrinsically excellent in large-area device fabrications. The film-forming kinetics for large-area devices remains unclear for organic solar cells. Here, the authors propose assembly-controlled kinetics with the assembly determined by molecular configuration and tuned via external effects, contributing to the screening of device fabrication conditions.

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