Loreleyn F Flores; Karem Y Tucto; Jorge A Guerra; Rolf Grieseler; Jan A Töfflinger; Andres Osvet; Miroslaw Batentschuk; Roland Weingärtner
Abstract
Amorphous silicon oxycarbide (a-SiCxOy) single doped with Yb3+ and co-doped with the couple Tb3+ - Yb3+ thin films were grown on crystalline silicon substrates by rf magnetron sputtering. The elemental composition in at. % is determined by energy dispersive spectroscopy and fourier transform infrared ...
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Amorphous silicon oxycarbide (a-SiCxOy) single doped with Yb3+ and co-doped with the couple Tb3+ - Yb3+ thin films were grown on crystalline silicon substrates by rf magnetron sputtering. The elemental composition in at. % is determined by energy dispersive spectroscopy and fourier transform infrared spectroscopy allows to investigate the chemical properties of the host. The concentration of Yb in the single doped sample was 3.5% and for the codoped samples (Yb, Tb) were (3%, 0.9%), (3.5%, 0.6%) and (4%, 0.6%), respectively. Post-deposition annealing treatments were made in order to induce optical activation of the rare earths. Conversion or absorption of high energy photons were analyzed by photoluminescence spectroscopy. The photoluminescence spectra show that for a given temperature range in the thermal annealing process, as well as for the appropriate rare earth concentrations the activation of Yb3+ and Tb3+ is enhanced. A strong reduction of the Tb3+ emission in contrast to the Yb3+ emission in the a-SiCxOy,:Tb:Yb samples at annealing temperature at 500°C suggests a energy transfer from Tb3+ to Yb3+ ions. Copyright © 2018 VBRI Press.
Uma Narang; Kumar K. Yadav; Soumee Bhattacharya; S.M.S. Chauhan
Abstract
The selected porphyrin acids such as 5-(4'-carboxyphenyl)-10,15,20-triphenylporphyrin, 5-(4'-carboxyphenyl)-10,15,20-tris-(4''-chlorophenyl)porphyrin, 5-(4'-carboxyphenyl)-10,15,20-tris-(4''-tertbutylphenyl)porphyrin and 5-(4'-carboxyphenyl)-10,15,20-(4''-pyridyl)porphyrin have been synthesised by reaction ...
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The selected porphyrin acids such as 5-(4'-carboxyphenyl)-10,15,20-triphenylporphyrin, 5-(4'-carboxyphenyl)-10,15,20-tris-(4''-chlorophenyl)porphyrin, 5-(4'-carboxyphenyl)-10,15,20-tris-(4''-tertbutylphenyl)porphyrin and 5-(4'-carboxyphenyl)-10,15,20-(4''-pyridyl)porphyrin have been synthesised by reaction of two aldehydes with pyrrole in propionic acid.The coupling of 5-(4'-carboxyphenyl)-10,15,20-triarylporphyrins with pentan-1,5-diol in presence of EDC and DMAP give unsymmetrical bisporphyrins, which were metallated with zinc acetate to give different porphyrin tweezers. The singlet oxygen efficiency of porphyrin tweezers as photosensitizers have been quantified by monitoring the transformation of1,3-diphenylisobenzofuran (DPBF) to 1,2-dibenzoylbenzene by UV-visible spectroscopy. The quantum yield of formation of singlet oxygen for different porphyrin tweezers have been examined. The electron withdrawing group containing porphyrin tweezer is a better photosensitizer than electron donating group in generation of singlet oxygen. Copyright © 2017 VBRI Press.
Akanksha Prakash; Shailesh Narain Sharma
Abstract
Indium Phosphide quantum dots (InP QDs) having various applications can be used for both LEDs and photovoltaics owing to its highly luminescent properties and energy harvesting potential respectively. In our work we have synthesized InP QDs using hot injection technique. Further post synthesis treatment ...
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Indium Phosphide quantum dots (InP QDs) having various applications can be used for both LEDs and photovoltaics owing to its highly luminescent properties and energy harvesting potential respectively. In our work we have synthesized InP QDs using hot injection technique. Further post synthesis treatment was given and InP/ZnS core shell nanocrystals were grown on InP core. Composites with P3HT conducting polymer were made in order to study the charge transfer/energy transfer phenomenon. InP and InP/ZnS QDs show an effective phenomenon of energy transfer and PL increment is observed in the case of composites. Whereas in the case of treated InP QDs a decrement in the PL was observed. Treatment results in removal of the surface defects and traps which help in effective charge transfer rather than energy transfer. Post synthesis treatment increases the monodispersity of the QDs which results in high quality QDs without any defects. With a simple post synthesis treatment,InP QDs can be used for both LEDs as well as photovoltaic applications. The future work involves the device fabrication of InP QDs and treated InP QDs for LED and solar cells respectively. Various characterization such photoluminescence, transmission electron microscopy, selected area diffraction was done in order to confirm the charge/energy transfer phenomenon. Copyright © 2016 VBRI Press.
