Ultrathin Double‐Shell Capsules for High Performance Photon Upconversion

Triplet-fusion-based photon upconversion capsules with ultrathin double shells are developed through a single dripping instability in a microfluidic flow-focusing device. An inner separation layer allows use of a brominated hydrocarbon oil-based fluidic core, demonstrating significantly enhanced upconversion quantum yield. Furthermore, a perfluorinated photocurable monomer serves as a transparent shell phase with remote motion control through magnetic nanoparticle incorporation.