Optically active chiral photonic crystals exhibiting enhanced fluorescence and circularly polarized luminescence

Photonic crystals with advanced, unique and well-defined functional nanostructures demonstrate exquisite controllable modulation in light harvesting and emission for unrivalled optical performance. Herein, through ingeniously integrating aggregation-induced emission (AIE) luminogens and chiral helical media into ordered periodic structures, the resulting optically active photonic crystal films exhibit an enhanced photoluminescence (PL) characteristic (increased to 2.2 times the original value) and distinctive emerging circular dichroism (CD) responses near the photonic bandgap (PBG) of the photonic crystal. The modulation of the PL intensity and CD signal peak position is precisely achieved by regulating the PBG by facilely tuning the size of the colloidal nanoparticles. Such an interesting phenomenon is mainly the consequence of the PBG edge enhancement effect (including the slow photon effect) and bandgap separation arising from chirality. Remarkably, the boosted fluorescence facilitates the synergistic effect of valid chirality transfer among achiral AIEgens and chiroptical media in a photonic matrix, which effectively contributes to the enhanced circularly polarized luminescence (CPL) activity, thereby expanding the potential applications of CPL-based optically active photonic materials in circularly polarizing emitting devices.