**1. Introduction**

64 Organic Light Emitting Devices

Digest of Technical Papers 40, 895 (2009).

[35] Y.-S. Tyan, Y. Q. Rao, X. F. Ren, R. Kesel, T. R. Cushman, W. J. Begley, N. Bhandari, Tandem Hybrid White OLED Devices with Improved Light Extraction. SID Symposium

> The development in organic light emitting diodes (OLEDs) has been one of the fastest growing research areas because of their potential applications in lighting and flat panel displays. Some commercialization of OLED devices such as lightings and displays has already been made. In particular, OLED displays are awaiting true commercialization toward large market. However, there are still several problems to be solved. Particularly two areas require ongoing improvements, 1) light extraction and 2) polarization. In this chapter the research activities in these two areas are summarized.
