658
23 Electricity-to-Light Conversion
Fig. 23.26 Typical OLED
design for a bottom and b
top emission
Fig. 23.27 a Transparent OLED panel. From [1973]. b Flexible OLED display. From [1974]. c 3 mm thin, 11 inch
diagonal OLED TV. From [1975]
The optimization of materials for the various functional layers is ongoing. The emission layer (EML)
is optimized for efficient radiative recombination for the design wavelength or wavelength range. The
highest efficacy of over 100 lm/W (Fig. 23.16) is achieved using phosphorescent materials (Sect. 18.6).
The contacts are optimized for high carrier injection efficiency and the transport layers are optimized
for high conductivity.
End of 2007 a transparent white OLED panel was introduced [1973] (Fig. 23.27a). Its transparency
is 55% and shall be improved in the future. A crucial point is the protection of the organic films
against moisture and air. The encapsulation by glass is very good. Flexible OLED panels with polymer
substrate and encapsulation have been demonstrated (Fig. 23.27b). OLED technology is currently used
for small displays in digital cameras and cellular phones. It enables very thin TV panels, only a few
mm thick (Fig. 23.27c) entering the mass market in 2010. An increase of the lifetime from 30,000 to
beyond 50,000 h is expected.
23 Electricity-to-Light Conversion
Fig. 23.26 Typical OLED
design for a bottom and b
top emission
Fig. 23.27 a Transparent OLED panel. From [1973]. b Flexible OLED display. From [1974]. c 3 mm thin, 11 inch
diagonal OLED TV. From [1975]
The optimization of materials for the various functional layers is ongoing. The emission layer (EML)
is optimized for efficient radiative recombination for the design wavelength or wavelength range. The
highest efficacy of over 100 lm/W (Fig. 23.16) is achieved using phosphorescent materials (Sect. 18.6).
The contacts are optimized for high carrier injection efficiency and the transport layers are optimized
for high conductivity.
End of 2007 a transparent white OLED panel was introduced [1973] (Fig. 23.27a). Its transparency
is 55% and shall be improved in the future. A crucial point is the protection of the organic films
against moisture and air. The encapsulation by glass is very good. Flexible OLED panels with polymer
substrate and encapsulation have been demonstrated (Fig. 23.27b). OLED technology is currently used
for small displays in digital cameras and cellular phones. It enables very thin TV panels, only a few
mm thick (Fig. 23.27c) entering the mass market in 2010. An increase of the lifetime from 30,000 to
beyond 50,000 h is expected.