Dynamic Surface Enrichment in Drying Thin-Film Binary Polymer Solutions

Abstract

Solution-cast, thin-film polymer composites find a wide range of applications, such as in the photoactive layer of organic solar cells. The performance of this layer crucially relies on its phase-separated morphology. Efficient charge-carrier extraction requires each of the components to preferentially wet one of the two electrodes. It is often presumed that the experimentally observed surface enrichment required for this is caused by specific interactions of the active ingredients with each surface. By applying a generalized diffusion model, we find the dynamics to also play an important role in determining which component accumulates at which surface. We show that for sufficiently fast evaporation the component with the smallest cooperative diffusivity accumulates at the free interface. Counterintuitively, depending on the interactions between the various components, this may be the smaller solute. Our comprehensive numerical and analytical study provides a tool to predict and control phase-separated morphologies in thin-film polymer composites.

Self‐Poled Sausage‐Like PVDF Nanowires Produced by Confined Phase Inversion as Novel Piezoelectric Nanogenerators

“…In order to shed light on how the tubelike confinement influences the mechanism of structure formation during lateral water ingress, we performed dynamic numerical simulations of the phaseinversion in a crosssectional, and rotationally symmetric, cylindrical geometry. Our calcula tions are performed using the same multicomponent free energyminimizing generalized diffusion approach [45][46][47][48][49][50] as we employed before for modeling the behavior of PVDF/water/ DMF ternary mixtures in thinfilm and fibers. [21,42] Its descrip tion is not repeated here.…”

Process optimization for microstructure-dependent properties in thin film organic electronics

“…The second processing parameter is the pattern of substrate surface chemistry [30]. Preferential wetting at the substrate can trigger surface-directed composition waves, influencing the final phase-separated morphology and often leading to surface enrichment layers [42,43]. Imposing a tailored pattern (through dip-pen nanolithography, for example) can effectively modulate the morphology development [44][45][46].…”

Efficiency enhancement of polyfluorene: Polystyrene blend light-emitting diodes by simultaneous trap dilution and β-phase formation

“…For more details and context, we refer to our prior work on evaporation-driven quenches of binary polymer solutions. 41,42 In summary, we have demonstrated how conformational changes in a luminescent conjugated polymer (polydioctylfluorene, PFO), brought about by blending with a flexible insulating polymer (polystyrene), drastically influences the optoelectronic behavior of the former. Blending induces the formation of PFO b-phase domains, consisting of fully extended chain segments with monomers oriented in a coplanar fashion.…”