Molecular Ordering and the Current-Voltage Characteristics of m-MTDATA Thin Films

Abstract:

Molecular ordering and current-voltage characteristics of vacuum-deposited m-MTDATA(4,4’,4’’-tris[N,-(3-methylphenyl)-N-phenylamino]triphenylamine), widely used as a hole injection material in OLEDs, thin films were investigated. Molecular ordering was induced by thermal annealing under electromagnetic field after deposition of m-MTDATA onto the pre-patterned ITO glass. AFM and XRD analysis were employed to characterize the topology and molecular ordering of m-MTDATA thin films. The XRD and AFM results show that m-MTDATA can be molecularly ordered by means of thermal annealing under electromagnetic field. Thermal annealing at 100°C was desirable to get a high degree of molecular ordering with dendritic grains. It was shown that molecular ordering as well as larger dendritic grains in the thin films influenced on improving the current-voltage characteristics and increasing the leakage current of the ITO/m-MTDATA/Al device. Electromagnetic field improved the surface roughness, as well. It is regarded that Rpv seems more significant than the other roughness parameters. Significantly lower Rpv(peak-to-valley roughness) obtained by both thermal annealing and electromagnetic field resulted in enhancing the stability of the current ITO/m-MTDATA/Al device. Ra(average roughness) and Rrms(root-mean-square roughness), however, did not significantly relate with leakage current.

• Periodical: Solid State Phenomena (Volumes 124-126)
• Pages: 427-430
• DOI: https://doi.org/10.4028/www.scientific.net/SSP.124-126.427
• Online since: June 2007
• Authors: Seong Oh, Do Soon Kang, Dae Won Park, Young Son Choe
• Keywords: Magnetic Field, m-MTDATA, Molecular Ordering, OLED, Thin Film

References

[1] M. I. Boamfa, P. C. M. Christianen, J. C. Maan, H. Engelkamp, and R. J. M. Nolte, Physica B. Vol. 343 (2001), p.294.

DOI: 10.1016/s0921-4526(00)00674-8

[2] Z. Ji, Y. Xiang and Y. Ueda, Prog. Org. Coat., Vol. 49 (2004), p.180.

[3] Z. Bao, A. J. Lovinger, and J. Dodabalapur, Appl. Phys. Lett., Vol. 69 (1996), p.3066.

[4] B. Bialek, I. G. Kim, and J. I. Lee, Thin Solid Films. Vol. 436 (2003), p.107.

[5] G. E. Collins, V. S. Williams, L. -K. Chau, K. W. Nebesny, C. England, P. A. Lee, T. Lowe, Q. Fernando, and N. R. Armstrong, Synth. Met., Vol. 54 (1993), p.351.

DOI: 10.1016/0379-6779(93)91081-c

[6] M. M. El-Nahass, Z. El-Gohary and H. S. Soliman, Opt. Laser Technol., Vol. 35 (2003), p.523.

[7] K. P. Khrishnakumar and C. S. Menon, Mater. Lett., Vol. 48 (2001), p.64.

[8] S. Yanagiya, S. Nishikata, G. Sazaki, A. Hoshino, K. Nakajima, and T. Inoue, J. Cryst. Growth. Vol. 254 (2003), p.244.

[9] Y. Choe, S. Park, D. Park, J. Chem. Eng. Japan, Vol. 38 (2005), p.600.

[10] Y. Choe, S. Park, D. W. Park, W. Kim, Macromolecular Research, Vol. 14 (2006), p.38.