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Electrical and optical characteristics; injection materials; red organic light-emitting diode; amorphous fluoropolymer; luminous efficiency; external quantum efficiency.

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.

Jong-Yeol Shin¹ Hyun-Min Choi² Hyeon-Seok Han² Jin-Woong Hong²

1. Department of Car Mechatronics, Sahmyook University, Nowon-Gu, Seoul, Korea (139-742)
2. Department of Electrical Engineering, Kwangwoon University, Nowon-Gu, Seoul, Korea (139-701)

Published

October 2011

Manuscript received

20 October 2010

Manuscript revised

25 February 2011

Accepted

15 April 2011