Coupling Photonic Bandgap Engineering with Photochromism for Upconversion Luminescence Modulation

However, conventional photochromism-induced luminescence regulation is usually governed by a reabsorption effect, leading to nonselective intensity modulation. Herein, PbWO₄:Yb³⁺/Er³⁺ inverse opal photonic crystals were fabricated through a template-assisted stepwise infiltration strategy, in which W- and Pb-containing precursor sols were sequentially introduced to avoid precipitation and ensure the formation of ordered photonic architectures.

The obtained PbWO₄:Yb³⁺/Er³⁺ inverse opals exhibit tunable photonic stop-bands and distinct structural colors. By matching the photonic bandgap with Er³⁺ emission bands, wavelength-selective inhibition and band-edge-enhanced upconversion luminescence were achieved, enabling the regulation of the red-to-green emission ratio. X-ray-induced photochromism originates from the synergistic effect of oxygen vacancy-related color center formation and polaron hopping associated with W⁶⁺/W⁵⁺ mixed-valence states, providing a reversible route for overall emission intensity modulation.