Abstract
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.
Highlights
Organic light-emitting diode (OLED) is a solid-state semiconductor device composed by superposition of different thin films to emission of light in different colors[1,2]
The comparison of I-V curves between organic light-emitting diode (OLED) mounted with PFTB emissive polymer diluted in chloroform and trichlorobenzene showed a significant difference in the performance of devices
Most reproducible results with aspect of diode curve. This fact was not completely observed in the electrical behavior of I-V curves for OLED devices mounted with PFTB diluted in chloroform. Another observation is related by tangent lines to the I-V curves for OLEDs mounted with PFTB diluted in trichlorobenzene, that revealed an easy method to obtain the threshold voltages[28]
Summary
Organic light-emitting diode (OLED) is a solid-state semiconductor device composed by superposition of different thin films to emission of light in different colors[1,2]. 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]. These devices can be divided in two different segments: polychromatic light, used as displays in smartwatches, smartphones and TVs14,15; and monochromatic light, used in ilumination or sinalization[16,17] (as foccus of this work)
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