Thin films find a variety of technological applications. Assembling thin films from atoms in the liquid phase is intrinsically a non-equilibrium phenomenon, controlled by the competition between thermodynamics and kinetics. We demonstrate here that microwave energy can assist in assembling atoms into thin films directly on a substrate at significantly lower temperatures than conventional processes, potentially enabling plastic-based electronics. Both experimental and electromagnetic simulation results show microwave fields can selectively interact with a conducting layer on the substrate despite the discrepancy between the substrate size and the microwave wavelength. The microwave interaction leads to localized energy absorption, heating, and subsequent nucleation and growth of the desired films. Electromagnetic simulations show remarkable agreement with experiments and are employed to understand the physics of the microwave interaction and identify conditions to improve uniformity of the films. The films can be patterned and grown on various substrates, enabling their use in widespread applications.

Nanobean SnO₂-embedded TiO₂ hollow submicrospheres as a scattering layer of dye-sensitized solar cells allow to simultaneously promote dye adsorption, light harvesting, and electron transport, leading to 28% improvement in the conversion efficiency compared to film-based SnO₂.