Effect of Pixellization on Efficiency and Stability of MEH-PPV Based Polymer Light-Emitting Diodes
- 1 Department of Materials and Metallurgical Engineering, Indian Institute of Technology, Kanpur, India
- 2 Samtel Centre for Display Technologies, Indian Institute of Technology, Kanpur, India
Abstract
Organic light-emitting diodes are generally depicted as sequential deposition of active layers and electrodes onto a substrate, but commercial devices are fabricated using pixellization technique, where an insulator layer is introduced between the indium tin oxide and organic layer to define the area of the active device. Here, we have inserted a layer of photoresist (thickness ~ 200 nm) at the edge of patterned anode (indium tin oxide) and between the anode and hole transport layer (Poly 3, 4-ethylenedioxythiophene poly styrenesulfonate) to examine its effect on the leakage current of organic light-emitting diode and on the electron-hole recombination ratio in the emission area, as a result increasing the luminance efficiency. Current leakage causes the loss of charges, which adversely affects the recombination of electrons and holes in the emitting zone and results in poorer luminance efficiency. In this paper, we report the effect of pixellization on current density-voltage, luminescence-voltage and degradation behavior of single layer Poly[2-methoxy-5-(2’-ethylhexyloxy)-1, phenylene vinylene] based organic light-emitting diodes. Devices with isolation layer have 30% higher external electroluminescence quantum efficiency and reduced device degradation in comparison to without isolation layer.
- N. K. Patel, S. Cina and J. H. Burroughes, “High-Efficiency Organic Light-Emitting Diodes,” IEEE Journal of Selected Topics in Quantum Electronics, Vol. 8, No. 2, 2002, pp. 346-361. doi:10.1109/2944.9991059
- Q. Xu, J. Ouyang, Y. Yang, T. Ito and J. Kido, “Ultrahigh Efficiency Green Polymer Light-Emitting Diodes by Nanoscale Interface Modification,” Applied Physics Letter, Vol. 83, No. 23, 2003, pp. 4695-4697. doi:10.1063/1.1630848
- S. Shi and D. Ma, “NaCl/Ca/Al as an Efficient Cathode in Organic Light-Emitting Devices,” Applied Surface Science, Vol. 252, No. 18, 2006, pp. 6337-6341. doi:10.1016/j.apsusc.2005.08.036
- S. H. Kim, J. Jang and J. Y. Lee, “Efficient Electron Injection in Organic Light-Emitting Diodes Using Lithium Quinolate/Ca/Al Cathodes,” Applied Physics Letter, Vol. 91, No. 10, 2007, pp. 103501-103503. doi:10.1063/1.2779105
- L. S. Hung, C. W. Tang and M. G. Mason, “Enhanced Electron Injection in Organic Electroluminescence Devices Using an Al/LiF Electrode,” Applied Physics Letters, Vol. 70, No. 2, 1996, pp. 152-154. doi:10.1063/1.118344
- S. H. Kim, J. Jang and J. Y. Lee, “Improvement in Power Efficiency in Organic Light Emitting Diodes Through Intermediate Mg:Ag Layer in LiF/Mg:Ag/Al Cathodes,” Electrochemical and Solid-State Letters, Vol. 10, No. 10, 2007, pp. J117-J119. doi:10.1149/1.2756337
- L. S. Hung and S. T. Lee, “Electrode Modification and Interface Engineering in Organic Light-Emitting Diodes,” Materials Science and Engineering: B, Vol. 85, No. 2-3, 2001, pp. 104-108. doi:10.1016/S0921-5107(01)00539-6
- R. Singh and M. Katiyar, “Polysilane Based Ultraviolet Light-Emitting Diodes with Improved Turn-On Voltage, Stability and Color Purity,” Synthetic Metals, Vol. 160, No. 17-18, 2010, pp. 1892-1895. doi:10.1016/j.synthmet.2010.07.005
- T. H. Yang, F. S. Juang, Y. S. Tsai, W. K. Kuo and M. Yokoyama, “Improvement of Luminance Efficiency by Insertion of Buffer Layers in Flexible Organic Light-Emitting Diodes,” Japanese Journal of Applied Physics, Vol. 45, 2006, pp. 3729-3732. doi:10.1143/JJAP.45.3729
- H. Becker, S. E. Burns and R. H. Friend, “Effect of Metal Films on the Photoluminescence and Electroluminescence of Conjugated Polymers,” Physical Review B, Vol. 56, No. 4, 1997, pp. 1893-1905. doi:10.1103/PhysRevB.56.1893
- P. E. Burrows, V. Bulovic, S. R. Forrest, L. S. Sapochak, D. M. McCarty and M. E. Thompson, “Reliability and Degradation of Organic Light Emitting Devices,” Applied Physics Letters, Vol. 65, No. 23, 1994, pp. 2922-2924. doi:10.1063/1.112532