Design, preparation and characterization of mixed semiconductor nanocrystal-salt crystals as extremely photostable and highly efficient light emitting materials for optical applications

点击翻译按钮获取中文摘要

Extremely high photoluminescence quantum yields (PL QY) and as high as possible photostability under application-relevant conditions are prerequisites for the use of semiconductor (SC) nanocrystals (NCs) as fluorescent labels and active components in optical devices. A typical approach to achieve and maintain a high PL QY is the encapsulation of SCNCs into robust and transparent matrices. For this purpose, we propose to use inorganic salt (e.g. NaCl, KCl, KJ, NH4J, etc.) crystals varying in crystal lattice and refractive index as matrices for embedding colloidal SCNCs of varying material composition and surface chemistry with emission in the visible and the infrared spectral region and the integration of these salt crystals into polymers. The protective and enhancing influence of inorganic salt crystals on the PL QY of SCNCs and their photostability was shown in first preliminary studies by us. The aim of the proposed project is the systematic study of the compatibility of our newly developed crystallization approaches with different types of SCNCs. Those will be prepared in aqueous and in organic solutions followed by characterization of the surface chemistries. We will apply sophisticated optical characterization methods, thereby comparing the optical properties and photochemical stability of the SCNCs in dispersion, in the salt matrix and, for selected systems, also as salt matrix-polymer composite materials. The NCs to be studied will include Cd-containing materials like CdTe; CdSe, CdHgTe or PbS and potentially less toxic materials like InP and CuInS(Se). Special emphasis will be dedicated to derive structure-property relations for the design of highly emissive and photostable SCNC-salt crystal composite structures potentially applicable for solid state lighting, luminescent solar concentrators as well as robust NIR and IR emission sources. For this purpose, we will also develop methods for the absolute measurement of PL QY of these differently scattering SCNC-salt crystal systems.