Articles written in Pramana – Journal of Physics
Volume 77 Issue 4 October 2011 pp 727-734 Research Articles
This study examined the electrical and optical properties of red OLEDs (organic lightemitting diodes) with a four-layer structure, ITO/amorphous fluoropolymer (AF)/$N,N'$--diphenyl$N,N'$-bis(3-methylphenyl)-1, 1-biphenyl-4,$4'$-diamine (TPD)/R-H:R-D/lithium fluoride (LiF)/Al, containing a hole injection material, AF (amorphous fluoropolymer) and an electron injection material, LiF. Compared to the basic structure (two-layer structure), the brightness and luminous efficiency of the four-layer structure, ITO/TPD/R-H:R-D/Al, increased approximately 100 times (30,000 lm/m2) and 150 times (51 lm/W), respectively, with an applied voltage. The excellent efficiency of the external proton was also increased 150 times (0.51%). That is, the hole and electron injection layers improved the surface roughness of ITO and Al, and the interfacial physical properties. In addition, these layers allowed the smooth injection of holes and electrons. The luminance, luminous efficiency and external quantum efficiency were attributed to an increase in the recombination rates.
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