We synthesized (CdSe)ZnS quantum dot (QD)–polymethylmethacrylate (PMMA) polymer composite and fabricated QD–polymer composite films. We produced the CdSe and (CdSe)ZnS QDs by direct colloidal chemical synthesis and the surface-passivation method—an overcoating of the dots with a larger-bandgap material. PMMA is transparent in the visible spectral range and was chosen as the embedding matrix for QDs. A 28%(wt/wt) of PMMA in MMA was the most appropriate concentration to produce a film of good quality and maximize the solubility of quantum dots without phase separation of the QDs from the matrix. We fabricated green or red light emitting (CdSe)ZnS QD–PMMA polymer composite film by combining the green or red light emitting (CdSe)ZnS dots with PMMA of high optical transparency in the visible region and spin-coating the composite solution. The fabricated green light emitting (CdSe)ZnS–PMMA composite film had a good quantum yield of 40% and a narrow emission band at 543 nm with a full width at half maximum of ∼35 nm. A white light emitting device can be fabricated by combining our green/red light emitting QD–polymer composites with a blue light emitting LED as an excitation source. Our QD–polymer composites can be applied to flexible coloured filters, large-area coloured wall-papers and full colour displays.

We produced core–shell (CdSe)ZnSe quantum dots by direct colloidal chemical synthesis and the surface-passivation method—an overcoating of the core CdSe with a larger-bandgap material ZnSe. The (CdSe)ZnSe quantum dots(QDs) play the role of a colour conversion centre. We call these quantum dots nanophosphors. We fabricated red light emitting hybrid devices of (CdSe)ZnSe QDs and a near-UV GaN LED by combining red light emitting (CdSe)ZnSe quantum dots (as a colour conversion centre) with a near-UV(NUV) GaN LED chip (as an excitation source). A few good red phosphors have been known for UV excitation wavelengths, and red phosphors for UV excitation have been sought for a long time. Here we tested the possibility of using (CdSe)ZnSe QDs as red nanophosphors for UV excitation. The fabricated red light emitting hybrid device of (CdSe)ZnSe and a NUV GaN LED chip showed a good luminance. We demonstrated that the (CdSe)ZnSe quantum dots were promising red nanophosphors for NUV excitation and that a red LED made of QDs and a NUV excitation source was a highly efficient hybrid device.

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Upon Cu doping into host semiconductor quantum dots (QDs), the intra-gap states inside band gap are generated, by which energy down-shifted photoluminescence (PL) with broad emissivity and large Stokes shift...

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