Nanopatterned Dual‐Carbon‐Dot Photonic Films With Enhanced Light Outcoupling

ABSTRACT

Carbon‐dot‐based luminescent films offer a low‐toxicity and solution‐processable alternative to conventional quantum‐dot emitters, but their implementation as solid‐state photonic films with controlled light extraction remains challenging. Here, we demonstrate nanopatterned dual‐carbon‐dot/poly(vinyl alcohol) (CD/PVA) films for enhanced directional light outcoupling. Blue‐emissive carbon dots (B‐CDs) and green‐emissive carbon dots (G‐CDs) were synthesized by microwave‐assisted carbonization and incorporated into water‐processable PVA matrices. The two CDs exhibited distinct heteroatom compositions, surface bonding configurations, and blue/green photoluminescence characteristics. Drop‐cast and spin‐coated films confirmed composition‐dependent blue–green emission in the solid state, while mixed B‐CD/G‐CD films showed spectral evolution and lifetime changes influenced by the coexistence of the two CD species. Nanoimprinted CD/PVA films with periodic surface structures produced angle‐dependent emission peaks under 355 nm Nd:YAG laser excitation, and the measured peak positions agreed with the calculated first‐order diffraction condition. Reference‐normalized emission analysis revealed approximately six‐fold relative angle‐dependent spectral enhancement at the calculated outcoupling angles in B‐CD‐rich films. These results establish nanopatterned dual‐CD/PVA films as water‐processable, carbon‐dot‐only photonic platforms in which solid‐state emission and light extraction can be jointly engineered through dual‐CD composition and nanoimprinted nanopattern design.