Confinement‐Enhanced Multi‐Wavelength Photon Upconversion Based on Triplet–Triplet Annihilation in Nanostructured Glassy Polymers. - Hu, Xueqian; Pollice, Luca; Ronchi, Alessandra; Roccanova, Marco; Mauri, Michele; Lardani, Davide; Vanhecke, Dimitri; Monguzzi, Angelo; Weder, Christoph (Advanced Science, 2025)