A general one-pot strategy for the synthesis of high-performance transparent-conducting-oxide nanocrystal inks for all-solution-processed devices

For all-solution-processed (ASP) devices, transparent conducting oxide (TCO) nanocrystal (NC) inks are anticipated as the next-generation electrodes to replace both those synthesized by sputtering techniques and those consisting of rare metals, but a universal and one-pot method to prepare these inks is still lacking. A universal one-pot strategy is now described; through simply heating a mixture of metal-organic precursors a wide range of TCO NC inks, which can be assembled into high-performance electrodes for use in ASP optoelectronics, were synthesized. This method can be used for various oxide NC inks with yields as high as 10 g. The formed NCs are of high crystallinity, uniform morphology, monodispersity, and high ink stability and feature effective doping. Therefore, the inks can be readily assembled into films with a surface roughness of 1.6 nm. Typically, a sheet resistance of 110 Ω sq-1 can be achieved with a transmittance of 88%, which is the best performance for TCO NC ink-based electrodes described to date. These electrodes can thus drive a polymer light-emitting diode (PLED) with a luminance of 2200 cdm-2 at 100 mA cm-2

Long-term stability of transparent n/p ZnO homojunctions grown by rf-sputtering at room-temperature

ZnO-based n/p homojunctions were fabricated by sputtering from a single zinc nitride target at room temperature on metal or ITO-coated glass and Si substrates. A multi-target rf-sputtering system was used for the growth of all oxide films as multilayers in a single growth run without breaking the vacuum in the growth chamber. The nitrogen-containing films (less than 1.5 at.% of nitrogen) were n-type ZnO when deposited in oxygen-deficient Ar plasma (10% O2) and p-type ZnO when deposited in oxygen-rich Ar plasma (50% O2). The all-oxide homojunction ITO/n-ZnO/p-ZnO/ITO/glass was fabricated in a single deposition run and exhibited visible transparency in the range of 75–85%. The n/p ZnO homojunctions, having metallic contacts, formed on conventionally processed substrates showed a fairly unstable behavior concerning the current-voltage characteristics. However, the same homojunctions formed on Si3N4-patterned substrates and stored in atmosphere for a period of five months were stable exhibiting a turn-on voltage of around 1.5 V. The realization of a room temperature sputtered transparent and stable ZnO homojunction paves the way to the realization of all-oxide transparent optoelectronic devices

Optoelectronic device based on Rare Earths electroluminescence

Màster en Nanociència i Nanotecnologia, Facultat de Física, Universitat de Barcelona, Curs: 2016-2017. Tutors: Oriol Blázquez, Sergi HernándezIn this Master Thesis, the fabrication and the structural, optical and electrical properties of Al/rare earth (RE)/Al/SiO2 and RE/SiO2 nanomultilayers have been studied. The nanomultilayers were deposited by means of e-beam evaporation on top of p-type Si substrates. Two different RE species were considered: Tb3+ and Eu3+ ions, as they exhibit a narrow and strong emission in the green and red spectral ranges, respectively. The main goal of the present work is achieving optical activation of those rare earth elements, and thus obtaining light emission from their intra-4f and 5d-to-4f shell transitions. Optical characterization indicates that optically active RE3+ ions had been successfully fabricated. The electrical and electroluminescence analysis yielded promising results to include this material in future applications of illumination and integrated emitting devices for optoelectronics

Optoelectronic device based on Rare Earths electroluminescence

Màster en Nanociència i Nanotecnologia, Facultat de Física, Universitat de Barcelona, Curs: 2016-2017. Tutors: Oriol Blázquez, Sergi HernándezIn this Master Thesis, the fabrication and the structural, optical and electrical properties of Al/rare earth (RE)/Al/SiO2 and RE/SiO2 nanomultilayers have been studied. The nanomultilayers were deposited by means of e-beam evaporation on top of p-type Si substrates. Two different RE species were considered: Tb3+ and Eu3+ ions, as they exhibit a narrow and strong emission in the green and red spectral ranges, respectively. The main goal of the present work is achieving optical activation of those rare earth elements, and thus obtaining light emission from their intra-4f and 5d-to-4f shell transitions. Optical characterization indicates that optically active RE3+ ions had been successfully fabricated. The electrical and electroluminescence analysis yielded promising results to include this material in future applications of illumination and integrated emitting devices for optoelectronics

Study of Thermoelectric Properties of Indium Silicon Oxide Thin Films

Thermoelectric devices, which convert heat into electricity, are regarded as an environmentally friendly alternative to fossil fuels used as the main resource for energy production. In the last few decades, transparent oxide semiconductors and conductors, namely Indium oxide-based materials, have been studied and applied in thin film transistors and solar cells. Nevertheless, this group of materials has also been studied for thermoelectric applications. In this dissertation, amorphous Indium silicon oxide (ISO) thin films were sputtered at room temperature on glass substrate, under different oxygen contents in the argon and oxygen mixture. The thermoelectric properties were evaluated as a function of deposition conditions and post-deposition annealing parameters (temperature and time). These properties were analysed and correlated with respective structural, morphological, optical, and electrical properties. For films deposited with no oxygen and annealed at 300 ºC for 24 h, the Seebeck coefficient and electrical resistivity at room temperature were 68:6 VK1 and 4:7 102 cm, respectively. Thin films deposited at higher oxygen percentages showed, in turn, very low conductivity values not being possible to measure the Seebeck coefficient. The maximum power factor achieved was 10 Wm1K2 for the aforementioned annealing conditions. A simultaneous increase of the Seebeck coefficient and electrical conductivity was also observed, mainly due to scattering mechanisms which enhanced the Seebeck coefficient. Although ISO thin films properties present a good stability when submitted to different post-deposition conditions, further studies need to be performed in order to optimise the thermoelectric properties and hence the power factor