Polymer light emitting device

Morii, K. et al. 2000. Characterization of light-emitting polymer devices prepared by ink-jet printing. Proc. 10th Int. Workshop on Inorganic and Organic Electroluminescence. pp. 357-360. 

Fig. 9.9. The schematic operation of a light emitting polymer device. Electrons in the conduction band and holes in the valence band are mutually captured, forming strongly bound exciton states. However, only the singlet excitons decay radiatively, emitting a photon. Triplet excitons decay nonradiatively, emitting phonons that is eventually wasted as heat.

Y. He, S. Gong, R. Hottori, and J. Kanicki, High performance organic polymer light-emitting heterostructure devices, Appl. Phys. Lett., 74 2265-2267, 1999. 

There is no reason why the same principle cannot be applied for light-emitting polymers as host materials to pave a way to high-efficiency solution-processible LEDs. In fact, polymer-based electrophosphorescent LEDs (PPLEDs) based on polymer fluorescent hosts and lanthanide organic complexes have been reported only a year after the phosphorescent OLED was reported [8]. In spite of a relatively limited research activity in PPLEDs, as compared with phosphorescent OLEDs, it is hoped that 100% internal quantum efficiency can also be achieved for polymer LEDs. In this chapter, we will give a brief description of the photophysics beyond the operation of electrophosphorescent devices, followed by the examples of the materials, devices, and processes, experimentally studied in the field till the beginning of 2005. 

Encapsulation of Light-Emitting Polymer Semiconductor Devices.577... 

ENCAPSULATION OF LIGHT-EMITTING POLYMER SEMICONDUCTOR DEVICES... 

A blue light-emitting electroluminescent device was claimed with an emission layer comprising a polymer matrix and a chromophoric component, which was either blended with or covalently attached to the polymer matrix. The chromophoric components were... 

As a conducting polymer, polyaniline has many electronics-related applications, such as rechargeable batteries (Tsutsumi et al. 1995), multilayer heterostructure light-emitting diode devices (Onoda Yoshino 1995), biosensors (Bartlett Whitaker 1987), elec-trochromic windows (Nguyen Dao 1989), and nonlinear optical materials (Papacostadi-nou Theophilou 1991). Polyaniline may be prepared from aniline by both electrochemi-... 

Methods 1 and 4 are currently the most promising ones for realizing multicolor devices. The latter method exhibits the advantage that the whole display can be built up with the same blue-light-emitting polymer LED, so that the same I-V response for all pixels (in contrast to the method 1) can be expected. 

In addition to the opportunity to increase the overall device performance in LEDs based on polymer blends,126 127 another interesting aspect is that their emission color can be internally converted.128-130 Based on blue-light-emitting polymers,131 therefore, any other emission color can be realized for those also, which intrinsically are difficult to achieve with pure conjugated polymers, as is the case for pure white132,133 and red134,135 emission colors. 

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