: Tae-Yun Lee, Jongho Lee, Yeonsang Park, Kyung-Sang Cho, Kyungtaek Min, and Heonsu Jeon

: Adv. Opt. Mater. 7(18), 1900209 (2019)

DOI https://doi.org/10.1002/adom.201900209 As a continuing effort to improve the performance of photonic crystal (PhC) phosphors—an engineered nanophotonic phosphor structure developed by the authors’ group—hereby two-dimensional (2D) PhC phosphor films are introduced. In particular, the excitation polarization dependence inherent to and suffered by the precedent one-dimensional PhC phosphors can be eliminated using a square lattice PhC structure due to its four-fold rotational symmetry. In addition, the thickness of the high index PhC backbone layer is intentionally increased so that dual excitation resonances occur for both the transverse-electric (TE) and transverse-magnetic (TM) waveguide modes, thereby effectively doubling the phosphor efficiency. 2D PhC phosphor structures were implemented and examined using colloidal quantum dots (CQDs) as phosphor material. Unlike conventional impurity-doped phosphor materials composed of micron-sized grains, nanometer-sized CQDs are structurally compatible with PhCs whose feature sizes are ~100 nm. Excitation-polarization-insensitive CQD fluorescence was observed to ~4 times enhanced at dual resonance wavelengths for the TE- and TM-guided modes. The validity of the observed results was confirmed through simulations.