Coffee-Ring Suppression in Inkjet-Printed Perovskite Films Enabled by a Shape-Anisotropic Nanorod Solute Strategy.

Achieving uniform perovskite thin films via inkjet printing remains a significant challenge due to the pervasive coffee-ring effect. Here, we present a solute engineering strategy that incorporates shape-anisotropic perovskite nanorods into a single-solvent ink formulation, effectively suppressing coffee-ring formation and yielding ultraflat films with an average roughness (Ra) as low as 0.226 nm. The anisotropic nanorod morphology modulates solute transport and deposition dynamics while also promoting the formation of directionally aligned domains. As a proof of concept, we demonstrate the linearly polarized perovskite films (polarization ratio ρ = 0.3357) by inkjet printing and the corresponding prototype electroluminescent devices. Although demonstrated with perovskite nanocrystals, this shape-anisotropic solute strategy may be broadly applicable to other functional materials, offering a universal route to uniform film formation and device integration.