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http://dx.doi.org/10.3740/MRSK.2010.20.6.294

Improving the Electrical and Optical Properties of Blue Polymer Light Emitting Diodes by Introducing TPBI Electron Transport Layer  

Gong, Su-Cheol (Department of Electronic Engineering, Dankook University)
Jeon, Chang-Duk (Department of Electronic Engineering, Dankook University)
Yoo, Jae-Hyouk (Nepes Corporation)
Chang, Ho-Jung (Department of Electronic Engineering, Dankook University)
Publication Information
Korean Journal of Materials Research / v.20, no.6, 2010 , pp. 294-300 More about this Journal
Abstract
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(4-methylphenyl)-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).
Keywords
polymer light emitting diode (PLED); electron transport layer; TPBI[2,2',2"-(1,3,5-Benzinetriyl)-tris(1-phenyl-1-H-benzimidazole)]; current efficiency; blue color;
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