10 documents found, page 1 of 1
Improving the reliability of power LEDs with diamond boards
Mendes, Joana C.; Rodrigues, Luis A.; Kyatam, Sushmitha; Alves, Luis N.; Pereira, LuizHigh power light emitting diodes (LEDs) are much more efficient than conventional light sources like filament bulbs. Nevertheless, heat is still generated, and this directly affects the reliability of these solid-state light (SSL) devices. In order to decrease the operating temperature, these LEDs can be assembled on metal core printed circuit boards (MCPCBs). However, in applications where stability/lifetime i...
Molybdenum oxide thin films grown on flexible ITO-coated PET substrates
Marciel, Alice; Graça, Manuel; Bastos, Alexandre; Pereira, Luiz; Suresh Kumar, Jakka; Borges, Joel; Vaz, F.; Peres, Marco; Magalhães, SergioMolybdenum oxide thin films were deposited on stiff and flexible substrates by reactive DC magnetron sputtering. Two sets of samples were prepared. The first with different O<sub>2</sub>/Ar flow rate ratios and the second, fixing the oxygen content, with different time of deposition. As the O<sub>2</sub>/Ar flow rate ratio varies from 0 up to 0.56, a threshold was found, ranging from crystalline to amorphous na...
Graded morphologies and the performance of PffBT4T-2OD:PC71BM devices using add...
Gaspar, Hugo; Parnell, Andrew J.; Pérez, Gabriel E.; Viana, J. C.; King, Stephen M.; Mendes, Adélio; Pereira, Luiz; Bernardo, GabrielThe impact of several solvent processing additives (1-chloronaphthalene, methylnaphthalene, hexadecane, 1-phenyloctane, and p-anisaldehyde), 3% v/v in o-dichlorobenzene, on the performance and morphology of poly[(5,6-difluoro-2,1,3-benzothiadiazol-4,7-diyl)-alt-(3,3"'-di(2-octyldodecyl)-2,2 ',5 ',22033,5 '',2"'-quaterthiophen-5,5"'-diyl)] (PffBT4T-2OD):[6,6]-phenyl-C71-butyric acid methyl ester (PC71BM)-based p...
A methodological proposal for a residential segregation study as a relational p...
Matias, Ítalo; Aquino, Carla Nogueira Patrão de; Pereira, Luiz; Silva, Fabio Freitas daThe article aims to analyze the residential segregation of the urban area of the 1st district of Campos dos Goytacazes, a city located in the North region of the state of Rio de Janeiro, Brazil, considering the subdistrict areas as units of analysis. For the study, a methodology of segregation analysis was adopted associating non-spatial indexes (dissimilarity and isolation indexes) with the spatial statistics ...
Thiophene- and carbazole-substituted N-Methyl-Fulleropyrrolidine acceptors in P...
Gaspar, Hugo; Figueira, Flávio; Strutyński, Karol; Melle-Franco, Manuel; Ivanou, Dzmitry; Tomé, João P. C.; Pereira, Carlos M.; Pereira, LuizThe impact of fullerene side chain functionalization with thiophene and carbazole groups on the device properties of bulk-heterojunction polymer:fullerene solar cells is discussed through a systematic investigation of material blends consisting of the conjugated polymer poly[(5,6-difluoro-2,1,3-benzothiadiazol-4,7-diyl)-alt-(3,3‴-di(2-octyldodecyl)-2,2′;5′,2″;5″,2‴-quaterthiophen-5,5‴-diyl)] (PffBT4T-2OD) as do...
PffBT4T-2OD based solar cells with Aryl-Substituted N-Methyl-Fulleropyrrolidine...
Gaspar, Hugo; Figueira, Flávio; Strutyński, Karol; Melle-Franco, Manuel; Ivanou, Dzmitry; Tomé, João P. C.; Pereira, Carlos M.; Pereira, LuizNovel C<sub>60</sub> and C<sub>70</sub> <i>N</i>-methyl-fulleropyrrolidine derivatives, containing both electron withdrawing and electron donating substituent groups, were synthesized by the well-known Prato reaction. The corresponding highest occupied molecular orbital (HOMO)/lowest unoccupied molecular orbital (LUMO) energy levels were determined by cyclic voltammetry, from the onset oxidation and reduction p...
Recent developments in the optimization of the bulk heterojunction morphology o...
Gaspar, Hugo; Figueira, Flávio; Pereira, Luiz; Mendes, Adélio; Viana, J. C.; Bernardo, GabrielOrganic photovoltaic (OPV) devices, made with semiconducting polymers, have recently attained a power conversion efficiency (PCE) over 14% in single junction cells and over 17% in tandem cells. These high performances, together with the suitability of the technology to inexpensive large-scale manufacture, over lightweight and flexible plastic substrates using roll-to-roll (R2R) processing, place the technology ...
Crystal Structure and Spectroscopic Studies of a Dimeric Europium( III) similar...
Coelho, Ana C.; Gomes, Ana C.; Fernandes, Jose A.; Almeida Paz, Filipe A.; Braga, Susana S.; Rino, Luis; Pereira, Luiz; Pillinger, MartynThe homodinuclear europium(III) -diketonate complex [Eu-2(bta)(4)(pypzCH(2)COO)(2)] (1) {bta = 1-benzoyl-3,3,3-trifluoroacetonate, pypzCH(2)COO = [3-(2-pyridyl)-1-pyrazolyl]acetate} was isolated after recrystallization of the crude product obtained from the reaction of [Eu(bta)(3)(H2O)(2)] with one equivalent of the ligand phenyl[3-(2-pyridyl)-1-pyrazolyl]acetate (pypzCH(2)CO(2)C(6)H(5)). A single-crystal X-ray...
Luminous efficiency enhancement of PVK based OLEDs with fac-[ClRe(CO)3(bpy)]
Mizoguchi, Sergio; Santos, Gerson; Andrade, Adnei; Fonseca, Fernando; Pereira, Luiz; Iha, NeydeThe luminous efficiency of organic light-emitting diodes based on poly(N-vinylcarbazole), PVK, was improved by adding fac-[ClRe(CO)3(bpy)], bpy = 2,2′-bipyridine, to PVK host. Emissive layers with various Re(I) complex/host ratio were employed and optoelectronic properties were compared with the single PVK device. The single PVK device exhibits a characteristic electroluminescence with blue emission, λmax 420 n...
Photo and electroluminescence behavior of Tb(ACAC)3phen complex used as emissiv...
Rino, Luís; Simões, W.; Santos, G.; Fonseca, F. J.; Andrade, A. M.; Deichmann, V. A. F.; Akcelrud, L.; Pereira, LuizThis work shows the luminescence properties of a rare-earth organic complex, the Tb(ACAC)3phen. The results show the 5D4 -> 7F3,4,5,6 transitions with no influence of any ligand emission. The photoluminescence excitation spectrum is tentatively interpreted by the ligands absorption. An OLED was made by thermal evaporation (total thickness of 1200 Å) using TPD and Alq3 as hole and electron transport layers, resp...