ABSTRACT:We fabricated blue polymer light-emitting diodes (PLEDs) with indium tin oxide (ITO)/PEDOT : PSS/PVK/PFO-poss/LiF/Al structures. All of the organic film layers were prepared by the spin-coating method on plasma and heat-treated ITO/glass substrates. The dependences of the optical and electrical properties of the PLEDs on the plasma and heat treatment of the ITO film and the introduction of poly(N-vinylcarbazole) (PVK) layer were investigated. The AFM measurements indicated that the surface roughness of the ITO transparent film was improved by the plasma and heat treatment. In the emission spectra, the intensity of the excimer peaks of the PFO-poss [polyhedral oligomeric silsesquioxane-terminated poly(9,9-dioctylfluorene)] emission layer were decreased for the PLED device with the PVK film layer compared with the one without the PVK layer. The maximum current density, luminance and current efficiency of the PLEDs were found to be about 470 mA/cm 2 , 486 cd/m 2 at an input voltage of 12 V and 0.55 cd/A at 100 cd/m 2 in luminance, respectively. The color coordinates (CIE chart) of the blue PLEDs were in the range of x ¼ 0.17 $ 0.20, y ¼ 0.13 $ 0.16, and the peak emission spectrum was about 430 nm, showing a good blue color.

Transparent conductive thin films of aluminum-doped zinc oxide (ZAO) were prepared by radio-frequency magnetron sputtering with ZAO (98 wt% ZnO, 2 wt% Al 2 O 3) as the ceramic target. The visible transmittance was investigated by ultraviolet-visible spectroscopy, the carrier concentration and Hall mobility were measured by the Van der Pauw method, and the phase composition was characterized by X-ray diffraction. The results show that the substrate temperature was a dominant factor of the properties, with the ZnO film deposited at a substrate temperature of 200 °C and a pure-argon gas pressure of 1 Pa exhibiting optimal performance. The resistivity and average transmittance in the wavelength range of 300-760 nm were 2.0 × 10 −4 Ω cm and 90.6%, respectively.

In this study, we fabricated a polymer light emitting diode (PLED) and investigated its electrical and optical characteristics in order to examine the effects of the PFO [poly(9,9-dioctylfluorene-2-7-diyl) end capped with N,N-bis(4methylphenyl)-4-aniline] concentrations in the emission layer (EML). The PFO polymer was dissolved in toluene ranging from 0.2 to 1.2 wt%, and then spin-coated. To verify the influence of the TPBI [2,2',2"-(1,3,5-Benzinetriyl)-tris(1-phenyl-1-H-benzimidazole)] electron transport layer, TPBI small molecules were deposited by thermal evaporation. The current density, luminance, wavelength and current efficiency characteristics of the prepared PLED devices with and without TPBI layer at various PFO concentrations were measured and compared. The luminance and current efficiency of the PLED devices without TPBI layer were increased, from 117 to 553 cd/m 2 and from 0.015 to 0.110 cd/A, as the PFO concentration increased from 0.2 to 1.0 wt%. For the PLED devices with TPBI layer, the luminance and current efficiency were 1724 cd/m 2 and 0.501 cd/A at 1.0 wt% PFO concentration. The CIE color coordinators of the PLED device with TPBI layer at 1.0 wt% PFO concentration showed a more pure blue color compared with the one without TPBI, and the CIE values varied from (x, y) = (0.21, 0.23) to (x, y) = (0.16, 0.11).