Search

This exploratory study was carried out with the objective to know the optical behavior of light-emitting diode (LED) lamps used and the temperature reached by electronic components that compose the driver (electronic circuit situated inside the body LED lamp) responsible to convert electrical alternating current from power line to direct current to operate the LED devices. Then, two different experiments were carried out with LED lamps. In the first experiment, 131 LED lamps used were chosen randomly and bought from household appliances store (bargain market product) presenting different nominal powers, 8, 10, 12 and 15 watts. All LED lamps were polarized at the power line at 127 V and revealed different optical behaviors, such as: not turn-on; flashing light (as strobe effect); flashing light (as strobe effect) with high intensity (more intense than normal); flashing light (as strobe effect) with low intensity (less intense than normal); fast turnon and turn-off only; and turn-on with low intensity of light (less intense than normal). The hypothesis for these behaviors can be attributed by three different behaviors: in lamps not turn-on, this failure can be attributed for dark spots that are created on the surface of LED device. In these lamps, all LED devices are electrically connected in serial. When a LED is inoperative, the electrical current is interrupted for all LED devices; damage to the electronic components caused by internal high temperature confined inside the lamp body during the operation causing electrical oscillations, as observed from different behaviors from flashing light, flashing light with high intensity, flashing light with low intensity and fast turn-on and turn-off only; swelling of the electrolytic capacitors causing low energy storage and varying the electrical current flow, the electrical current for other electronic components altered the normal optical behavior of the LED lamps. In the second experiment, the temperatures of electronic components located in driver were obtained out of body lamp revealing: from 33 (lowest temperature attributed to inductor) to 52.5ºC (highest temperature attributed to electrolytic capacitor). These temperature values represent the ideal or normal condition of operation for electronic components, but, when they are operating inside the lamp body, the found temperature values increased considerably. This characteristic can be better evidenced by strong color change (caused by accumulative temperature during the elapsed days used) on the printed circuit board used in the driver.

In this work, circular economy was investigated for commercial indium tin oxide (ITO) thin films deposited on glass substrates obtained from degraded organic light-emitting diodes (OLED). These devices were assembled and polarized at laboratory in a previous work. For each substrate, with geometry 2.5 × 2.5 cm, four OLEDs with active area of 3 × 3 mm were set up. These OLED devices were assembled with ITO as the electrode anode and successive depositions of other materials (layer-by-layer), to form the complete structure. To obtain the recovered ITO, all layers were removed from the samples containing the OLEDs previously mounted, remaining only the ITO thin films, that were cleaned with commercial product together with the received ITO/glass samples. Both samples were compared using some techniques, such as: colorimetry, electrical resistance, and Raman spectroscopy. A methodology with light-emitting diode (LED) device polarized emitting light crossing the ITO thin films was used, and the luminance with chromaticity coordinates was obtained, revealing the good transparency of the thin films. Electrical resistance of recovered ITO revealed five higher orders of magnitude in comparison to the one of received ITO. This fact can be tributed to a poly(3,4-ethylenedioxythiophene) doped with poly(styrenesulfonate) (PEDOT:PSS) layer, causing corrosion of the ITO thin films during the assembly of OLEDs or loss of the field lines created during the electrical measurements by probes of four-point probe. Raman spectroscopy did not show satisfactory results in the chemical composition analyses of the samples, but it indicated good cleaning process of the samples before the analyses.

Transparent conductive oxides (TCOs) known as indium tin oxide (ITO) and fluorine tin oxide (FTO) deposited on glass were compared by different techniques and also as anodes in organic light-emitting diode (OLED) devices with same structure. ITO produced at laboratory was compared with the commercial one manufactured by different companies: Diamond Coatings, Displaytech and Sigma-Aldrich, and FTO produced at laboratory was compared with the commercial one manufactured by Flexitec Company. FTO thin films produced at laboratory presented the lowest performance measured by Hall effect technique and also by I-V curve of OLED device with low electrical current and high threshold voltage. ITO thin films produced at laboratory presented elevated sheet resistance in comparison with commercial ITOs (approximately one order of magnitude greater), that can be related by a high number of defects as discontinuity of the chemical lattice or low crystalline structure. In the assembly of OLED devices with ITO and FTO produced at laboratory, neither presented luminances. ITO manufactured by Sigma-Aldrich company presented better electrical and optical characteristics, as low electrical resistivity, good wettability, favorable transmittance, perfect physicalchemical stability and lowest threshold voltage (from 3 to 4.5 V) for OLED devices.

In this work, organic light-emitting diode (OLED) devices were mounted using the structure: glass (as substrate)/indium tin oxide (ITO) (as anode)/poly(3,4-ethylenedioxythiophene) doped with poly(styrenesulfonate) (PEDOT:PSS) (as hole transport layer)/poly[9,9-dioctifluorene-alt-bis-tienilene(benzotiadiazole)] (PFTB) (as luminescent material)/aluminum-doped zinc oxide (AZO) (as electron transport layer)/aluminum (as cathode). The PFTB was synthetized at laboratory and diluted in different organic solvents as chloroform and trichlorobenzene. The I-V curves of OLED devices showed that the trichlorobenzene used to dillute the PFTB improved the performance for OLED devices promoting the highest electrical current of ≈50 mA and the lowest range of thresold voltage from ≈2.5 to 5 volts, while the device OLEDs mounted with PFTB dilutted in chloroform presented maximum electrical current of ≈23 mA and range of thresold voltage from ≈5 to 8 volts. A hypothesis that explain these results can be attributed to the boiling point of the organic solvent of trichlorobenzene (≈214.4ºC) to be higher than the one of the chloroform (≈61.1ºC), favoring better rearrangement of the polymer chains of PFTB and interfaces between thin films PFTB/PEDOT:PSS and PFTB/AZO improving the injection of charges (holes and electrons) inside the OLEDs devices.

In this work, a spinner apparatus was mounted with some characteristics, as: low cost, easy operation, compact size, easy adaptation into the little glove box systems, no vacuum pump and low maintenance. Firstly, three different fans wereanalyzed to be used in thespinner apparatus. Then, the Arduino electronic circuit was analyzed and programmed to control the rotation speed using a pulse width modulation (PWM) and steps of acceleration with the signal distortion (caused by pulse width modulation) of thefan intern tachometer. After, the interface between the user and spinner apparatus was performed with information about: navigation through the menus; input of process parameters as rotation speed; rotation time and calibration menu. Successive depositions of organic thin films to assembly of OLED deviceswere used with the spinner apparatus. The experiment compared ITO (indium tin oxide) thin filmanodes with sheet resistances of 8 and 12 ?/? supplied by different manufacturersin the structure of the OLEDs.I-V curves of OLED devices showed that the ITO/glass of 12 ?/? presented better results with low variabilityand highest current values. All OLED devices presented some luminance showing the efficiency of spinner apparatus.

In a homemade UV-Ozone generator, different ignition tubes extracted from HID mercury vapor lamps were investigated, namely: 80, 125, 250 and 400 watts. The performance of the generator in function of the type of the ignition lamp was monitored by the measurements of the ozone concentration and the temperature increment. The results have shown that the 400 W set up presented the highest ozone production, which was used in the treatment of indium tin oxide (ITO) films. Polymer light emitting diodes were assembled using ITO films, treated for 10, 20 and 30 min, as an anode. The overall results indicate improvement of the threshold voltage (reduction) and electroluminescence of these devices.

This work aims the development of a compact spinner to be used inside the glove-box chamber to deposition of polymeric thin films used in the build of OLED devices. Initially, ten fans extracted of microcomputers were tested with commercial multi-voltage power supply. Four fans were selected based on the standard deviation of speed. A variable power supply was also built in order to get a more detailed response in terms of electrical current and speed in function of applied voltage. The fan that showed less variation of speed with applied voltage was selected for deposition tests using polymeric photoresist solution on the ITO (indium tin oxide) coated glass. This polymer was deposited by spin-coating at different speeds: 1000, 2000, 3000 and 4000 rpm and dried for the thicknesses measurement revealing good uniformity. Finally, three OLED devices were assembled with 2000 and 3000 rpm and the layers were dried under the same conditions. In the structure of the devices were used the materials deposited layer-by-layer:glass/ITO/PEDOT:PSS/ Polyfluorene (PFpf)/Al. The OLED devices revealed blue light electroluminescence. The I-V curves showed better performance for OLED devices mounted at 2000 rpm with higher current density and similar appearance to the diode curve.

Low cost UV-Ozone reactor using a high pressure mercury vapor lamp of 80 watts without outer bulb showed good results for treatment of ITO films used as anode electrode in the assembly of P-OLED (polymer-organic light emitting diode) devices. This study revealed 20 minutes as effective treatment time and it was verified also that the effect of UV-Ozone treatment loses its efficiency as the elapsed time increases. It was analyzed with measurements of contact angle using a droplet of PEDOT:PSS polymer. P-OLEDs devices were mounted with architecture: ITO/PEDOT:PSS/PVK/Alq3/Al. The PVK polymer was diluted in organic solvent of 1,2,4-trichlorobenzene with concentrations of: 5, 10, 20 and 30 mg/mL. Results revealed better performance of P-OLED devices for concentration of 5 mg/mL resulting in lower threshold voltage, elevation of electrical current and similar diode curve.