Directional Fluorescence Spectral Narrowing in All-Polymer Microcavities Doped with CdSe/CdS Dot-in-Rod Nanocrystals

We report on the fluorescence properties of high optical quality all-polymer planar microcavities embedding core−shell dot-in-rod CdSe/CdS nanocrystals. Properly tuned microcavities allow a 10-fold sharpening of the nanocrystals fluorescence spectrum, resulting in a reduction of the bandwidth from 24 to 2.4 nm, which corresponds to a quality factor larger than 250. A 5-fold peak photoluminescence intensity enhancement is measured, while the overall number of emitted photons is reduced. Time-resolved photoluminescence and quantum yield for microcavities and suitable references show the presence of two decays related to differences in nanocrystal size distribution. The slower decay rate, which becomes faster when the nanocrystals are embedded into the microcavity, is assigned to longer nanorods with emission spectrally overlapped to the cavity mode. Conversely, the short-living component, which is assigned to an impurity of shorter nanorods, remains unaffected by the microcavity.