Abstract
The development of phosphor devices free of heavy metal or rare earth elements is an important issue for environmental reasons and energy efficiency. Different mixtures of ZnO nanocrystals with Cs2Mo6I8(OOC2F5)6 cluster compound (CMIF) dispersed into polyvinylpyrrolidone matrix have been prepared by very simple and low cost solution chemistry. The resulting solutions have been used to fabricate highly transparent and luminescent films by dip coating free of heavy metal or rare earth elements. The luminescence properties of solution and dip-coated films were investigated. The luminescence of such a system is strongly dependent on the ratios between ZnO and CMIF amounts, the excitation wavelength and the nature of the system. By varying these two parameters (ratio and wavelength), a large variety of colors, from blue to red as well as white, can be achieved. In addition, differences in the luminescence properties have been observed between solutions and thin films as well as changes of CMIF emission band maximum wavelength. This may suggest some possible interactions between the different luminophore centers, such as energy transfer or ligands exchange on the Mo6 clusters.
Highlights
More and more attention is being paid to environmental and energy efficiency issues,[1] e.g. the production of low carbon energy from ‘green’ resources, reducing energy consumption by improving device performances, or developing new more environmentally friendly materials
We investigated the luminescence properties of a mixture of zinc oxide (ZnO) nanocrystals and Cs2Mo6I8(OOC2F5)6 cluster-based compound dispersed into a PVP matrix in solution and dip-coated thin films
The 550 nm emission band is attributed to the photoluminescence generated by defects in ZnO nanocrystals,[32,33,34,35,36,37] while the 650 nm emission band is attributed to the [Mo6Ii8(OOCC2F5)a6]2- cluster units.[20]
Summary
More and more attention is being paid to environmental and energy efficiency issues,[1] e.g. the production of low carbon energy from ‘green’ resources, reducing energy consumption by improving device performances, or developing new more environmentally friendly materials. New nanocomposite solutions or thin films may have potential applications, as well as in light devices [2,3,4] or luminescent solar concentrator for photovoltaic devices.[5] Chalcogenides quantum dots [6,7] and rare-earth (RE) doped materials [8,9,10] are considered as the most promising inorganic phosphor candidates They may have some issues related to their toxicity in the case of quantum dots, which contain heavy metal (HM), or their high cost and environmental and availability problems due to their extraction in the case of RE doped materials. We observed different emission behaviors of the mixtures in solution or in thin films, which suggests some interactions between the different luminescent centers
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