Enhanced visible light absorption in a photocatalytic thin film from a decoupled photonic crystal

The optical and photocatalytic properties of a photonic crystal structure were examined to elucidate the origin of the enhanced visible light absorption from semiconductor photonic crystals. Both an enhancement in visible light absorption and an increase of the photoactivity of the semiconductor photocatalyst were found when a photonic crystal layer was decoupled from the photocatalytic film. The decoupling clearly shows that the optical enhancement arose from the dielectric mirror effect of the photonic crystal. As such, the enhancement was maximized by matching the high light absorbance region of photocatalytic semiconductors with the characteristic photonic band gap of the decoupled photonic crystal layer under various illumination conditions. For enhanced visible light photocatalytic activity, the decoupled photonic crystal layer does not have to be made from the same light-harvesting materials, but can be synthesized by a wide range of materials for ease of the fabrication process.