for lighting applications
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The Nano Crystal Research Research for lighting applications involves the synthesis of various semiconductor nano crystals, characterization, and the actual device construction and testing. Nano crystal synthesis: The colloidal nanocrystals are synthesized by wet chemistry methods. Highly mono disperse QDs are synthesized in a coordinating surfactant mixture. In order to synthesize mono disperse particles is the nucleation separated from the particle growth. This is achieved by a rapid injection of a relative high concentration of precursors in a high temperature surfactant mixture. The concentration and high temperature will give burst to a formation of very small particles. The relative slow particle growth is continued a lower temperature, this method results in high quality mono disperse nano crystals. The investigated semiconductor nano crystals in this project are: cadmium selenide (CdSe); cadmium sulfide (CdS); lead selenide (PbSe), and several core shell particles CdSe/ZnS, CdSe/CdS, CdTe/CdS, CdTe/CdSe. Crystal shape control: The surfactant composition, together with precursor concentration and temperature as parameters can be used to control the shape of the nano crystals. The particles made in this project are mainly focused at spherical and rod shaped crystals, however other shapes are also possible. The QRs show a narrow band linear polarized emission, they can be aligned at an macroscopic scale as we have show in Advanced Materials, 2005, 17, 1436, where oriented QRs where used in hybrid polymer/QR LED. Device construction and testing: The QD and QRs are applied as a new type of chromophores in light emitting diodes (LEDs). This part of the research is focused on device design and construction, followed by optical and electronic measurements.
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