LEDs, organic

The fractal-like organization led, therefore, to conductivity measurements at three different scales (1) the macroscopic, mm-size core of nanotube containing material, (2) a large (60 nm) bundle of nanotubes and, (3) a single microbundle, 50 nm in diameter. These measurements, though they do not allow direct insights on the electronic properties of an individual tube give, nevertheless, at a different scale and within certain limits fairly useful information on these properties. 

Figure 9-25. Field-induced tunneling relative t]uanlunt efficiencies of organic LEDs calculated for various carrier mobilities and barrier heights (I KT , ,=,=0.2 2...//,= If) /( =I0"8,...

In summary, a fundamental model for the current flow in organic LED does not exist but there are several different models which seem to describe the l/V characteristics of the various different organic LEDs reasonably well. 

The set-up of an organic LED at first sight appears to be very simple. However, in actuality the preparation of LEDs is rather sophisticated and requires careful and clean processing where many steps have to be performed in a dust- and oxygen-free environment. The performance of the LEDs strongly depends on the preparation conditions and this therefore complicates any comparisons made of different groups on the same LEDs. This must be taken into account as well as... 

The theory of charge recombination in organic LEDs has been elaborated recently [110-113]. 

Biisslcr et ai [110-113] treated charge recombination in organic LEDs in terms of chemical kinetics. The probability of recombination depends on the ratio of recombination rate ynp-np (where y represents a bimolecular rate constant) and the transition time (itr=dlpE) of the charge carriers through the device. 

The same equations as for the electron-only devices can be applied to describe the 1/V characteristics for organic LEDs based on Alq3 (in single and multihetero layer devices) 82. ... 

The design of the organic LEDs should be optimized so that the double charge injection factor and the probability for singlet exciton formation is near to unitv... 

K. Hutchison, J. Gao, G. Schick, Y. Rubin, F. Wudl, Bucky Light Bulbs White Light Electroluminescence from a Fluorescent C60 Adduct-Single Layer Organic LED , J. Am Chem. Soc. 1999,121,5611-5612. 

P. Posch, R. Fink, M. Thelakkat, and H.-W. Schmidt, A comparison of hole blocking/electron transport polymers in organic LEDS, Acta Polym., 47 487-494, 1998. 

M. Greczmiel, P. Strohriegl, M. Meier, and W. Briitting, Polymethacrylates with pendant oxadiazole units synthesis and application in organic LEDs, Macromolecules, 30 6042-6046,1997. 

Z. Liu, O.V. Salata, and N. Male, Improved electron injection in organic LED with lithium quinolate/aluminium cathode, Synth. Met., 128 211-214 (2002). 

T. Wakimoto, Y. Yonemoto, J. Funaki, M. Tsuchida, R. Murayama, H. Nakada, H. Matsumoto, S. Yamamura, and M. Nomura, Stability characteristics of quinacridone and coumarin molecules as guest dopants in the organic LEDs, Synth. Met., 91 15-19 (1997). 

J.E. Malinsky, G.E. Jabbour, S.E. Shaheen, J.D. Anderson, A.G. Richter, T.J. Marks, N.R. Armstrong, B.K. Pulak Dutta, and N. Peyghambarian, Self-assembly processes for organic LED electrode passivation and charge injection balance, Adv. Mater., 11 227-231, 1999. 

C.C. Wu, S.D. Theiss, G. Gu, M.H. Lu, J.C. Sturm, S. Wagner, and S.R. Forrest, Integration of organic LEDs and amorphous Si TFTs onto flexible and lightweight metal foil substrates, IEEE Electron. Device Lett., 18 609-612, 1997. 

T Wakimoto, R Murayama, K Nagayama, Y Okuda, H Nakada, and T Tohma, Organic LED Dot-Matrix Display, Proceedings of the Society for Information Displays, Technical Digest 27, San Diego, 1996, pp. 849-852. 

X Zhou, J He, LS Liao, M Lu, XM Ding, XY Hou, M Zhang, XQ He, and ST Lee, Real-time observation of temperature rise and thermal breakdown processes in organic LEDs using an IR imaging and analysis system, Adv. Mater., 12 265-269, 2000. 

M Arai, K Nakaya, O Onitsuka, T Inoue, M Codama, M Tanaka, and H Tanabe, Passive matrix display of organic LEDs, Synth. Met., 91 21-25, 1997. 

MS Weaver, WD Bennet, C Bonham, PE Burrows, GL Graff, ME Gross, M Hall, RH Hewitt, SY Mao, E Mast, PM Martin, LA Michalski, T Ngo, K Rajan, MA Rothman, and JA Silvernail, Flexible Organic LEDs, Proceedings of the Society for Information Display, Electronic Information Displays Conference, London, 2000, pp. 191-222. 

C. Cimico, Electro-Optical Characterization of Organic LEDs, Photonics Spectra, July 66-68, 2003. 

The use of conjugated light emitting polymers in the construction and commercialisation of organic LEDs is described in the section 3.8.6 on electroluminescence phenomena of Chapter 3. The rapid expansion of the development work on LEDs has inevitably led to the examination of luminescent conjugated polymers as materials for constructing laser diodes. 

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