Reflection and transmission two-way structural colors†
Management of reflection and transmission two-way structural colors is significant in color displays, projections, and anticounterfeiting. Here, inspired by the Lycurgus Cup, we fabricated photonic crystals with opal and inverse opal structures with controlled thickness, which show reflection and transmission two-way structural colors. In order to balance the reflection and transmission intensities, we first studied the effect of the order layer thickness on the reflection and transmission spectra and found that a thickness of about 5 μm can help the structural colors achieve high saturation in both directions. The photonic crystal film built with 295 nm SiO2 spheres shows bright red and green structural colors in the reflection and transmission directions, respectively. These two-way colors can be projected onto substrates, similar to a transflective color filter. The color displays can be tuned by adjusting the angle between the incident light and the sample. Furthermore, we also patterned the photonic crystal film with two-way structural colors, which shows clear patterns and rich colors in both directions. The photonic crystals assembled on a small wine glass display two-way structural colors similar to those of the Lycurgus Cup. More importantly, a flexible inverse opal photonic crystal film with two-way structural colors was also fabricated, which can be applied in multimode anticounterfeiting. This work will greatly expand the application field of photonic crystals in double sided displays, transflective color filters and anticounterfeiting.