Research Projects

Phase separation and structure formation in fluids receives new and sustained research interest in the presence of evaporation; driven by its applications in optimised production of solar cells. Currently, new promising technologies of solution-processed organic and perovskite solar cells are growing for significant market impact. The efficiency of these devices can be greatly improved by tuning the nanomorphology formed during their fabrication. The underlying physical processes involve wetting, evaporation, deposition and drying of thin liquid films. In this project, we will study computationally morphology formation in evaporating fluid mixtures in connection with the dynamic evolution of structures which determine the final coating morphology. Our mesoscale simulation results will be analyzed within the framework of phase-field theory. The main focus is on understanding the influence of various system parameters, e.g., fluid temperature, evaporation rate, composition ratios of different components of the mixture, patterning of substrates on the morphology. The outcome of this project will thus improve the current understanding of the process-structure relationship for organic solar cells and assist their production. Inter alia, our project also finds technological applications in spray coating of thin films, agricultural industry for controlled pesticides spraying, printing and drying. While phase separation upon a rapid temperature quench is well studied, structure formation due to a ‘concentration’ quench, as driven by evaporation, is still not clearly understood. Particularly, the mechanism of domain growth, growth laws, universality of the associated growth exponents remain as open questions. The outcomes of this project will contribute to the fundamental understanding of these important issues. Another significant topic in this direction is heat transfer coupled to structure for- mation processes which for drying can enable crack formation. Heat transfer leads to time- dependent inhomogeneous temperature fields in a system. We will study the non-equilibrium structure formation in the presence of temperature gradients in a confined fluid via atomistic molecular dynamics simulations. Special empasis will be given to the role of tempera- ture gradient, thermal diffusivity and Soret effect on the formation and growth of domain morphology.