Optical properties for N,N’-bis (lnaphyhly)N,N’-diphenyl-1,1’-biphenyl-4,4’-diamine and tris (8-hydroxyquinolinato) aluminum in organic light emitting devices

Mei Yee Lim, Wan Mahmood Mat Yunus, Zainal Abidin Talib, Anuar Kassim
DOI: 10.4236/ns.2010.26078                

Abstract

The optical properties of N,N’-bis (Inaphthyl)N,N’-diphenyl-1,1’-biphenyl-4,4’-diamine (NPB) and tris (8-hydroxyquinolinato) aluminum (Alq3) organic materials used as hole transport and electron transport layers in organic light-emitting devices (OLED) have been investigated. The NPB and Alq3 layers were prepared using thermal evaporation method. The results show that the energy band gap of Alq3 is thickness independence while the energy band gap of NPB decreases with the increasing of sample thickness. For the case of photoluminescence the Alq3 with thickness of 84 nm shows the highest relative intensity peak at 510 nm.

Keywords

Energy Band Gap; N, N’-Bis (Inaphthyl) -N, N’-Diphenyl-1, 1’-Biphenyl-4, 4’-Diamine Tris (8 Hydroxyquinolinato) Aluminum; Organic Light Emitting Diode; Photoluminescence

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1]	Van Slyke, S.A., Chen, C.H. and Tang, C.W. (1996) Organic electroluminescent devices with improved stability. Applied Physics Letters, 69(15), 2160-2162.
[2]	Hung, L.S., Tang, C.W. and Mason, M.G. (1997) Enhanced electron injection in organic electroluminescence devices using an Al/LiF electrode. Applied Physics Letters, 70(2), 152-155.
[3]	O’Brien, D.F., Baldo, M.A., Thompson, M.E. and Forrest, S.R. (1999) Improved energy transfer in electrophosphorescent devices. Applied Physics Letters, 74(3), 442-444.
[4]	Lee, C.B., Uddina, A., Hua, X. and Andersson, T.G. (2004) Study of Alq3 thermal evaporation rate effects on the OLED. Materials Science & Engineering B, 112(1), 14-18.
[5]	Kido, J. and Okamoto, Y. (2002) Organo lanthanide metal complexes for electroluminescent materials. Chemical Reviews, 102(6), 2357-2368.
[6]	Silva, V.M. and Pereira, L. (2006) The nature of the electrical conduction and light emitting efficiency in organic semiconductors layers: The case of [m-MTDATA] – [NPB] – Alq3 OLED. Journal of Non-Crystalline Solids, 352(50-51), 5429-5436.
[7]	Burrows, P.E., Forrest, S.R. and Thompson, M.E. (1997) Prospects and applications for organic light-emitting devices. Current Opinion in Solid State & Materials Science, 2(2), 236-243.
[8]	Hung, L.S. and Chen, C.H. (2002) Recent progress of molecular organic electroluminescent materials and devices. Materials Science & Engineering R, 39(5-6), 143222.
[9]	Zhang, Z.F., Deng, Z.B., Liang, C.J., Zhang, M.X. and Xu, D.H. (2003) Organic light-emitting diodes with a nanostructured TiO2 layer at the interface between ITO and NPB layers. Displays, 24(4-5), 231-234.