Browse > Article

Recrystallization-Free Coating of Small Molecules for OLEDs  

Hong, Gi-Young (School of Electrical & Electronic & Communication Engineering, Korea University of Technology and Education)
Lee, Jin-Young (School of Electrical & Electronic & Communication Engineering, Korea University of Technology and Education)
Shin, Dong-Kyun (School of Electrical & Electronic & Communication Engineering, Korea University of Technology and Education)
Park, Jong-Woon (School of Electrical & Electronic & Communication Engineering, Korea University of Technology and Education)
Seo, Hwa-Il (School of Electrical & Electronic & Communication Engineering, Korea University of Technology and Education)
Publication Information
Journal of the Semiconductor & Display Technology / v.15, no.2, 2016 , pp. 38-42 More about this Journal
Abstract
We investigate the solution coating process of organic small molecules that are easily recrystallized in a solvent. The spin-coated films of small molecule N,N'-diphenly-N,N'-bis(1,1'-biphenyl)-4,4'-diamine (NPB) exhibit many aggregations on the surface and thus poor surface morphology. To tackle it, we have added a chain-entangled polymer poly(N-vinylcarbazole) (PVK) into the NPB solution. It is found that a small amount of PVK indeed prohibits the recrystallization of NPB in a solvent. By the addition of PVK (30 wt%), the peak-to-peak roughness of the films is reduced from 262 nm down to 2.7 nm, which is even lower than that (~5.1 nm) of the polymer film. It is also demonstrated that OLED with the PVK-mixed NPB film shows higher current and power efficiencies, compared to OLED with the NPB or PVK film. It is attributed that the addition of PVK into NPB suppresses the occurrence of leaky channels induced by the recrystallization phenomenon.
Keywords
OLED; spin coating; recrystallization; hybrid organic materials; surface roughness;
Citations & Related Records
연도 인용수 순위
  • Reference
1 R. Chesterfield, A. Johnson, C. Lang, M. Stainer, and J. Ziebarth, "Solution-coating technology for AMOLED displays," Inf. Display, vol. 27 pp. 24-30, 2011.
2 R. R. Sondergaard, M. Hosel, and F. C. Krebs, "Roll-to-roll fabrication of large area functional organic materials," J. Polym. Sci. Part B: Polym. Phys., vol. 51, pp. 16-34, 2013.   DOI
3 T.-W. Lee, T. Noh, H.-W. Shin, O. Kwon, J.-J. Park, B.-K. Choi, M.-S. Kim, D. W. Shin, and Y.-R. Kim, "Characteristics of Solution-Processed Small-Molecule Organic Films and Light-Emitting Diodes Compared with their Vacuum-Deposited Counterparts," Adv. Funct. Mater., vol. 19, pp. 1625-1630, 2009.   DOI
4 L. Duan, L. Hou, T.-W. Lee, J. Qiao, D. Zhang, G. Dong, L. Wang, and Y. Qiu, "Solution processable small molecules for organic light-emitting diodes," J. Mater. Chem., vol. 20, pp. 6392-6407, 2010.   DOI
5 J. Lee, N. Chopra, S.-H. Eom, Y. Zheng, J. Xue, F. So, and J. Shi, "Effects of triplet energies and transporting properties of carrier transporting materials on blue phosphorescent organic light emitting devices," Appl. Phys. Lett., vol. 93, pp. 123306, 2008.   DOI
6 D.-H. Lee, J. S. Choi, H. Chae, C.-H. Chung, and S. M. Cho, "Highly efficient phosphorescent polymer OLEDs fabricated by screen printing," Displays, vol. 29, pp. 436-439, 2008.   DOI
7 S. I. Ahn, W. K. Kim, S. H. Ryu, K. J. Kim, S. E. Lee, S.-H. Kim, J.-C. Park, and K. C. Choi, "OLED with a controlled molecular weight of the PVK (poly(9-vinylcarbazole)) formed by a reactive ink-jet process," Org. Electron., vol. 13, pp. 980-984, 2012.   DOI
8 D.-H. Lee, Y.-P. Liu, K.-H. Lee, H. Chae, and S. M. Cho, "Effect of hole transporting materials in phosphorescent white polymer light-emitting diodes," Org. Electron, vol. 11, pp. 427-433, 2010.   DOI