Flexible organic crystal-quantum dot hybrids with adjustable waveguides†

Organic molecular crystals have shown great potential in integrated photonics due to their long-distance ordered packing structures and optical merits. However, single-component organic crystals often emit mono-color light, limiting full exploitation of their advantages. Herein, we demonstrate a modular approach to impart multicolor luminescence to organic single crystals while preserving their crystallinity. Semiconductor quantum dots (QDs) with distinguishable fluorescence are conformally coated onto flexible organic crystals via a layer-by-layer electrostatic self-assembly strategy. The resultant hybrid crystals integrate emissions from both QDs and original crystals, and can function as flexible optical waveguides with adjustable outputs. Exciting different positions of the hybrid crystals leads to multicolor output signals at the crystal end, which can be decoded into encrypted messages. This work provides a facile strategy to combine the advantages of QDs and organic crystals for diverse photonic applications.