Opaline backreflector coating in dye-sensitized solar cell.

Photonic crystals are ordered nanostructures that are designed to manipulate the propagation of light. The periodicity of a photonic crystal can be engineered to be highly reflective at selected wavelengths. In this work, a mono-layer and double-layer colloidal photonic crystal film were self-assembled on a glass substrate to be used as backreflectors in a dye-sensitized solar cell (DSSC).

Kinetic stages of single-component colloidal crystallization.

To harness the full potential of colloidal self-assembly, the dynamics of the transition between colloids in suspension to a colloidal crystalline film should be better understood. In this report, the structural changes during the self-assembly process in a vertical configuration for colloids in the size range 200-400 nm are monitored in situ, using the transmission spectrum of the colloidal assembly treated as an emergent photonic crystal. It is found that there are several sequential stages of colloidal ordering: in suspension, with a larger lattice parameter than the solid state, in a close-packed wet state with solvent in the interstices, and, finally, in a close-packed dry state with air in the interstices.