Rodrigues, J, Mata D, Pimentel A, Nunes D, Martins R, Fortunato E, Neves AJ, Monteiro T, Costa FM.
2015.
{One-step synthesis of ZnO decorated CNT buckypaper composites and their optical and electrical properties}, may. Materials Science and Engineering: B. 195:38–44.
Abstractn/a
Santos, L, Nunes D, Calmeiro T, Branquinho R, Salgueiro D, Barquinha P, Pereira LÍ, Martins R, Fortunato E.
2015.
{Solvothermal synthesis of gallium-indium-zinc-oxide nanoparticles for electrolyte-gated transistors.}, jan. ACS applied materials {&} interfaces. 7:638–46., Number 1
AbstractSolution-processed field-effect transistors are strategic building blocks when considering low-cost sustainable flexible electronics. Nevertheless, some challenges (e.g., processing temperature, reliability, reproducibility in large areas, and cost effectiveness) are requirements that must be surpassed in order to achieve high-performance transistors. The present work reports electrolyte-gated transistors using as channel layer gallium-indium-zinc-oxide nanoparticles produced by solvothermal synthesis combined with a solid-state electrolyte based on aqueous dispersions of vinyl acetate stabilized with cellulose derivatives, acrylic acid ester in styrene and lithium perchlorate. The devices fabricated using this approach display a ION/IOFF up to 1 × 10(6), threshold voltage (VTh) of 0.3-1.9 V, and mobility up to 1 cm(2)/(V s), as a function of gallium-indium-zinc-oxide ink formulation and two different annealing temperatures. These results validates the usage of electrolyte-gated transistors as a viable and promising alternative for nanoparticle based semiconductor devices as the electrolyte improves the interface and promotes a more efficient step coverage of the channel layer, reducing the operating voltage when compared with conventional dielectrics gating. Moreover, it is shown that by controlling the applied gate potential, the operation mechanism of the electrolyte-gated transistors can be modified from electric double layer to electrochemical doping.
Pavan, M, Rühle S, Ginsburg A, Keller DA, Barad H-N, Sberna PM, Nunes D, Martins R, Anderson AY, Zaban A, Fortunato E.
2015.
{TiO2/Cu2O all-oxide heterojunction solar cells produced by spray pyrolysis}, jan. Solar Energy Materials and Solar Cells. 132:549–556.
AbstractHere we present for the first time a TiO2/Cu2O all-oxide heterojunction solar cell entirely produced by spray pyrolysis onto fluorine doped tin oxide (FTO) covered glass substrates, using silver as a back contact. A combinatorial approach was chosen to investigate the impact of the TiO2 window layer and the Cu2O light absorber thicknesses. We observe an open circuit voltage up to 350mV and a short circuit current density which is strongly dependent of the Cu2O thickness, reaching a maximum of {\~{}}0.4mA/cm2. Optical investigation reveals that a thickness of 300nm spray pyrolysis deposited Cu2O is sufficient to absorb most photons with an energy above the symmetry allowed optical transition of 2.5eV, indicating that the low current densities are caused by strong recombination in the absorber that consists of small Cu2O grains.
Nunes, D, Santos L, Duarte P, Pimentel A, Pinto JV, Barquinha P, Carvalho PA, Fortunato E, Martins R.
2015.
{Room temperature synthesis of Cu₂O nanospheres: optical properties and thermal behavior.}, feb. Microscopy and microanalysis : the official journal of Microscopy Society of America, Microbeam Analysis Society, Microscopical Society of Canada. 21:108–19., Number 1
AbstractThe present work reports a simple and easy wet chemistry synthesis of cuprous oxide (Cu2O) nanospheres at room temperature without surfactants and using different precursors. Structural characterization was carried out by X-ray diffraction, transmission electron microscopy, and scanning electron microscopy coupled with focused ion beam and energy-dispersive X-ray spectroscopy. The optical band gaps were determined from diffuse reflectance spectroscopy. The photoluminescence behavior of the as-synthesized nanospheres showed significant differences depending on the precursors used. The Cu2O nanospheres were constituted by aggregates of nanocrystals, in which an on/off emission behavior of each individual nanocrystal was identified during transmission electron microscopy observations. The thermal behavior of the Cu2O nanospheres was investigated with in situ X-ray diffraction and differential scanning calorimetry experiments. Remarkable structural differences were observed for the nanospheres annealed in air, which turned into hollow spherical structures surrounded by outsized nanocrystals.