In this work, we analyze the temperature of the LED lamp of white emission with 9 W with or without the influence of the cooling process using a fan. The investigation was carried out by seven different methods: (1) Analysis of temperature close to LEDs inside the bulb (diffuser); (2) Analysis of temperature on LEDs without bulb; (3) Analysis of temperature on LEDs without bulb with cooling using a fan; (4) Analysis of temperature on LEDs board out of body lamp without bulb; (5) Analysis of temperature on LEDs board out of body lamp without bulb with cooling using a fan. This last analysis 5 exhibited better results, decreasing the significant temperature on the LED surface from ≈130ºC (found in analysis 2) to ≈45ºC. Due to good results exhibited in analysis 5, it was used in the illuminance measurements of the LED lamp without cooling in the analysis 6, and with a fan as analysis 7. Both results compared showed that using a fan had a great influence, and difference on the illuminance values by elapsed time from ≈47,000 lux without a fan (analysis 6) to ≈55,300 lux with fan (analysis 7), and also the use of a fan exhibited the lowest time of stabilization in 1 minute only.
Zinc oxide (ZnO) nanoparticles (NPs) were synthesized by different methods known as Pechini and Sol-Gel. It was observed during the experiments significant differences comparing these methods as: particle size, time applied, crystallinity and chemical residues generated by-products. The NPs were analysed by X-ray diffraction (XRD), ultraviolet-visible (UV-Vis.) absorption and Raman spectroscopy techniques. X-Ray Difractograms showed peaks corresponding to hexagonal wurtzite crystalline structure. It was observed that NPs obtained by the Pechini showed better homogeneity and crystallinity; these presented average size of 115 nm. The NPs produced by Sol-Gel method showed crystallites with smaller average size of 8 nm. The band gap energy (Eg) obtained using UV-Vis for ZnO NPs synthesized by Pechini was 3.39 eV. Still, the results for Sol-Gel method with 5 and 10 hours of reactions were 3.53 eV and 3.55 eV respectively. Raman data obtained by Pechini and Sol-Gel Methods showed characteristics peaks. The obtained data confirmed the ZnO phase samples and the proportional relationship to the enlargement with the intensity of peaks E 2 High ˜ 438 cm -1 , as evidenced by literature. These results lead to the applicability of both NPs in optoelectronic and fluorescent applications.
This research aimed to build hybrid solar cells, based on Grätzel method. We used the Polyethylene Terephthalate (PET) polymer as a substrate containing a layer of Indium Tin Oxide (ITO). Films of ZnO nanoparticles (ZnO NPs) synthesized by Pechini Method, and four different dyes were tested: Congo Red (CR), Bromocresol Green (BG), Acridine Orange (AO) and a Ruthenium Complex (RC). ZnO NPs were analyzed by XRD, which generated peaks corresponding to hexagonal wurtzite crystalline structure. We also conducted analysis by UV-Vis. Spectroscopy and Transmission Electron Microscope (TEM). Rietveld analysis determined the crystal size of 115.23 ± 28.16 nm. The deposition of ZnO and dye thin films were made through spin-coating. The electrical properties of the formed films were characterized with Van der Pawn method. Efficiency in converting light in electricity under an OSRAM 20W light bulb was tested after the devices were built. The smaller sheet resistance results were obtained for material containing: PET/ITO/ZnO/CR and PET/ITO/ZnO/AO. As expected, the best open-circuit voltage (Voc) results reached were 64 and 73 mV to CR and AO, respectively. Therefore, the results demonstrated satisfactory interaction between the ZnO-Dye-Electrolyte layers.
Este trabalho mostra o estudo de dispositivos comerciais de diodo emissor de luz (diodo emissor de luz) e a influência de sua temperatura para alcançar o máximo desempenho. Nos experimentos, duas condições diferentes foram comparadas: (a)LEDs polarizados e imersos em água corrente com 12,5; 25 e 50 mL; e (b) LEDs polarizados em ar atmosférico. Os resultados revelaram que a água corrente pode ser um bom método para redução da temperatura aumentando significantemente os valores de corrente e luminância. Os LEDs polarizados imersos em água corrente revelaram também que 12,5 mL promoveu maior corrente de 228 mA e luminância máxima de 2.146.000 cd/m 2 , enquanto o LED polarizado no ar atmosférico apresentou apenas corrente de 68 mA e luminância abaixo de 1.700.000 cd/m 2 . Este aumento de desempenho mostrou uma pequena diferença nas coordenadas de cromaticidade para obter a mais pura emissão de cor branca.
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