We have fabricated transparent white organic light emitting diode (WOLED) for lighting application based on a hybrid
white OLED and a phosphorescence white OLED. For the hybrid WOLED, a blue fluorescence emitting layer (FLEML)
and green and red phosphorescence emitting layers (PH-EMLs) have been used in the device structure of
ITO/hole transporting layer
(HTL)/PH-EMLs/interlayer/FL-EML/ETL/LiF/Al. The balanced emissions from the FLEML
and the PH-EMLs have been obtained by using appropriate carrier (hole) trapping effects in the PH-EMLs, which
resulted in external and power efficiencies of 15 % and 27 lm/W, respectively, at a luminance of 1000 cd/m2 without any
out-coupling enhancement. The Commission Internationale de L'Eclairage (CIE) coordinates of this hybrid WOLED is
(0.43,0.44) with color rendering index (CRI) of 80 and correlated color temperature (CCT) of 3200 K, respectively, in
the bottom emission structure. Based on this hybrid WOLED, we established highly efficient transparent WOLED by
introduction of a transparent cathode, and obtained over 19 lm/W of power efficiency at a total luminance of 1000 cd/m2
as well as over 60 % of transmittance at 550 nm with the conventional glass encapsulation. Moreover, when the
phosphorescent white OLED was combined with a transparent cathode, the power efficiency was reached up to 24 lm/W
of power efficiency at a total luminance of 1000 cd/m2.
An electrically driven light emission from silicon is a long-standing problem in silicon photonics. Recently, significant progress has been made using silicon quantum dots embedded in silicon nitride thin films, transparent doping layers and electrodes, and surface modified structures. This paper provides an overview of progress in the device physics and fabrications of the nanocrystal silicon light emitting diodes including new device structures to improve the light extraction efficiency as well as highlights in growth of silicon quantum dots and their quantum confinement effects.