Improving the Performance of Organic Light Emitting Diodes by Doping PEDOT:PSS

Abstract:

Organic light emitting diodes (OLEDs) have the potential to compete with other rivals in applications of lighting and small size displays because of low power consumption. To achieve commercial standard, however, the luminance efficiency and device lifetime of the OLEDs still need to be improved. This work characterizes the performance of OLEDs improved by Poly (3,4-ethylenedioxythiophene) poly (styrenesulfonate) (PEDOT:PSS). PEDOT:PSS films are deposited on ITO glass by spin coating at the first, and then the hole transporting layer and electron transporting layer of the OLED materials N, N '-bis (naphthalene-1-yl)-N, N '-bis (phenyl) benzidine/tris-(8-hydroxyquinoline) aluminum (NPB/Alq₃) are thermally evaporated with 1 Å/s deposition rate. The thickness effects of the PEDOT:PSS on the OLED performance are studied. The result shows that PEDOT:PSS effectively improves the luminance of the OLEDs, where 40 nm thick PEDOT:PSS increases 12% and 30 nm thick increases 31% luminance, respectively. Furthermore, the effects of the PEDOT:PSS on the mechanical properties of the OLED are also studied.

• Periodical: Advanced Materials Research (Volumes 881-883)
• Pages: 1130-1135
• DOI: https://doi.org/10.4028/www.scientific.net/AMR.881-883.1130
• Online since: January 2014
• Authors: Tsai Cheng Li, Rwei Ching Chang*, Yan Jun Chen
• Keywords: Luminance, OLED, PEDOT:PSS, Residual Stress

References

[1] C.W. Tang, S.A. Van Slyke, Organic electroluminescent diodes, Applied Physics Letter 51 (1987) 913–915.

[2] H.Y. Yu, X.D. Feng, D. Grozea, Z.H. Lu, R.N.S. Sodhi, A.M. Hor, Surface electronic structure of plasma-treated indium tin oxides, Applied Physics Letter 78 (2001)2595–2597.

DOI: 10.1063/1.1367897

[3] G. Liu, J.B. Kerr, S. Johnson, Dark spot formation relative to ITO surface roughness for polyfluorene devices, Synthetic Metals 144 (2004)1–6.

DOI: 10.1016/j.synthmet.2004.01.011

[4] H. Ohta, M. Orita, M. Hirano, H. Hosono, Surface morphology and crystal quality of low resistive indium tin oxide grown on yittriastabilized zirconia, Journal of Applied Physics 91 (2002) 3547–3550.

DOI: 10.1063/1.1448873

[5] Y. Leterrier, L. Medico, F. Demarco, J.A.E. Manson, U. Betz, M.F. Escola, Mechanical integrity of transparent conductive oxide films for flexible polymer-based displays, Thin Sol Films 460 (2004) 156–166.

DOI: 10.1016/j.tsf.2004.01.052

[6] T.P. Nguyen, P. Le Rendu, P.D. Long, S.A. De Vos, Chemical and thermal treatment of PEDOT: PSS thin films for use in organic light emitting diodes, Surface & Coatings Technology 180 (2004) 646–649.

DOI: 10.1016/j.surfcoat.2003.10.110

[7] T. Aernouts, P. Vanlaeke, W. Geens, J. Poortmans, P. Heremans, S. Borghs, Printable anodes for flexible organic solar cell modules, Thin Sol Films 451 (2004) 22–25.

DOI: 10.1016/j.tsf.2003.11.038

[8] S.A. Carter, J.C. Scott P.J. Brock, Enhanced luminance in polymer composite light emitting devices, Applied Physics Letter 71 (1997) 1145–1147.

DOI: 10.1063/1.119848

[9] B.W. Xiao, Y.F. Shang, M. Meng, C.N. Li, Enhancement of hole injection with an ultra-thin Ag2O modified anode in organic light emitting diodes, Microelectronics Journal 36 (2005) 105–108.

DOI: 10.1016/j.mejo.2004.11.006

[10] F.S. Li, Z.J. Chen, C.L. Liu, Q.H. Gong, Improvement in performance of organic light-emitting diodes by adjusting charge-carrier mobility in organic/inorganic hybrid hole transporting layer, Chemical Physics Letters 412 (2005) 331–335.

DOI: 10.1016/j.cplett.2005.07.011

[11] G.F. Wang, X.M. Tao, R.X. Wang, Fabrication and characterization of OLEDs using PEDOT: PSS and MWCNT nanocomposites, Composites Science and Technology 68 (2008) 2837–2841.

DOI: 10.1016/j.compscitech.2007.11.004

[12] C.J. Chiang, S. Bull, C. Winscom, A. Monkman, A nano-indentation study of the reduced elastic modulus of Alq3 and NPB thin-film used in OLED devices, Organic Electronics 11 (2010) 450–455.

DOI: 10.1016/j.orgel.2009.11.026

[13] K. Suzuki, N. Hashimoto, T. Oyama, J. Shimizu, Y. Akao, H. Kojima, Large scale and low resistance ITO films formed at high deposition rates, Thin Solid Films 226 (1993) 104-109.

DOI: 10.1016/0040-6090(93)90213-9

[14] D.R. Cairns, R.P. Witte, D.K. Sparacini, S.M. Sachsman, D.C. Paine, G.P. Crawford , R. Newton, Strain-dependent electrical resistance of tin-doped indium oxide on polymer substrates, Applied Physics Letters 76 (2000)1425- 1427.

DOI: 10.1063/1.126052

[15] C. Guillen, J. Herrero, Comparison study of ITO thin films deposited by sputtering at room temperature onto polymer and glass substrates, Thin solid films 480–481 (2005) 129–132.

DOI: 10.1016/j.tsf.2004.11.040

[16] E.H. Kim, C.W. Yang, J.W. Park, Improving the delamination resistance of indium tin oxide (ITO) coatings on polymeric substrates by O2 plasma surface treatment, Current Applied Physics 10 (2010) S510–S514.

DOI: 10.1016/j.cap.2009.12.028

[17] I.C. Noyan, J.B. Cohen, Residual Stress, Measurement by Diffraction and Interpretation, Springer-Verlag, New York, (1987).

[18] U. Welzel, J. Ligot, P. Lamparter, A.C. Vermeulen, E.J. Mittemeijer, Stress analysis of polycrystalline thin films and surface regions by X-ray diffraction, Journal of Applied Crystallography 38 (2005) 1-29.

DOI: 10.1107/s0021889804029516

[19] J. S. Kim, F. Cacialli, R. Friend, Surface conditioning of indium-tin oxide anodes for organic light-emitting Diodes, Thin Solid Films 445 (2003)358-366.

DOI: 10.1016/s0040-6090(03)01185-4