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White OLED used in lighting. White OLEDs emit white light that is brighter, more uniform and more energy efficient than that emitted by fluorescent lights. White OLEDs also have the true-color qualities of incandescent lighting. Because OLEDs can be made in large sheets, they can replace fluorescent lights that are currently used in homes and buildings. Their use could potentially reduce energy costs for lighting.
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An Organic Light Emitting Diode (OLED) is a device composed of an organic layer that emits lights in response to an electrical current. Organic light emitting diodes have advanced tremendously over the past decades. The different manufacturing processes of the OLED itself to several advantages over flat panel displays made with LCD technology which...
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... Basically, the light-emitting layer is composed by organic material located between two inorganic thin films, the anode (transparent and semiconductor material deposited on transparent substrate) and the cathode (metallic conductor) 3,4 . Researches have been carried out with the objective to find materials that present efficient performance as low threshold voltage and high luminance, but the operating voltage is still elevated if compared with common inorganic light-emitting diode (LED) devices 5,6 . Another problem is related to the prolonged use in OLED technology, because the organic materials have short lifetime, caused principally by water and oxygen in the ambient air 7 , leading to dark spots or bur-in deffects 8,9 . ...
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.
... Basically, an OLED is made up of several layers that composed organic matters, sandwiched between two electrodes, anode and cathode [22,23]. It can be designed to emit a single color of light, white light or even tunable colors. ...
Organic Light Emitting Diode (OLED) is a new promising technology in lighting and display applications due to the advantages offered by the organic over inorganic materials. Nevertheless, the devices poor environmental stability and growth of dark spots has been a major concern for OLED devices. Based on the past literatures, several failure mechanisms have been proposed, suggesting that there is no particular model for the mechanisms of dark spots formation. In addition, the formation of dark spots is relatively obscure and unpredictable. On top of that, comprehensive reviews on the dark spots formation mechanism and the prevention methods are very limited at the current moment. Yet, both information are truly critical to be obtained and understood for OLED future development works. Thus, this paper reviewed particularly on the root cause formation of dark spots mechanisms in OLED devices. The dark spots are mainly formed due to the presence of foreign impurities and pinholes, as well as due to high current intensity. These root factor of elements will further enhance the degradation of OLED via bubble formations, electro-migrations, crystallizations and many other damaging processes. A few prevention steps have been discussed in order to reduce and prevent the dark spots from occurring such as the proper material selection and conducting the fabrication process in a controlled environment.
... Basically, an OLED is made up of several layers that composed organic matters, sandwiched between two electrodes, anode and cathode [22,23]. It can be designed to emit a single color of light, white light or even tunable colors. ...
Organic Light Emitting Diode (OLED) is a new promising technology in lighting and display applications due to the advantages offered by the organic over inorganic materials. Nevertheless, the devices poor environmental stability and growth of dark spots has been a major concern for OLED devices. Based on the past literatures, several failure mechanisms have been proposed, suggesting that there is no particular model for the mechanisms of dark spots formation. In addition, the formation of dark spots is relatively obscure and unpredictable. On top of that, comprehensive reviews on the dark spots formation mechanism and the prevention methods are very limited at the current moment. Yet, both information are truly critical to be obtained and understood for OLED future development works. Thus, this paper reviewed particularly on the root cause formation of dark spots mechanisms in OLED devices. The dark spots are mainly formed due to the presence of foreign impurities and pinholes, as well as due to high current intensity. These root factor of elements will further enhance the degradation of OLED via bubble formations, electro-migrations, crystallizations and many other damaging processes. A few prevention steps have been discussed in order to reduce and prevent the dark spots from occurring such as the proper material selection and conducting the fabrication process in a controlled environment.
Considering the structural stability for active-matrix organic light-emitting diode (AMOLED) application, the reliability of lamination interfaces has become a major concern. The comprehensive influence of structural design integrated with material selections should be carefully examined and estimated. The layout effect of embedded pattern defined layer (PDL) plays an important role in the actual AMOLED architecture. To address the issue of stress-induced failure mechanism of PDL under external loads due to external bending, fracture mechanics-based finite element analysis integrated with Tsai–Hill criterion is utilized in this research. Simulated results indicate that the declined thickness and 45° oblique angle design for PDL prevents the failure occurrence of concerned interfaces. Notably, multiple neutral axis (NA) occurs when an extra-low Young’s modulus of pressure-sensitive adhesive (PSA) is considered. Multiple NA design prevents brittle fracture failure occurrence in gas barrier architecture, while these multiple NAs shift to adjust to the foregoing location. Accordingly, a proper arrangement of these multiple NAs in AMOLED packaging encapsulation through the selection of material characteristics and stacked thickness of PSA thin film has the advantage to enhance structural reliability.
