Improvement of Efficiencies and Lifetimes of White Light-emitting Organic Diodes Using a Novel Co-evaporated 'hole-confining' Structure

Download or read book Improvement of Efficiencies and Lifetimes of White Light-emitting Organic Diodes Using a Novel Co-evaporated 'hole-confining' Structure written by Aparna Rakurthi and published by . This book was released on 2010 with total page 119 pages. Available in PDF, EPUB and Kindle. Book excerpt: Organic light-emitting diodes (OLEDs) have received much attention in recent years due to their potential for applications in full color displays and solid state lighting. White organic light-emitting devices in particular, play a significant role in: 1) the realization of full color displays due to the flexibility they offer in obtaining any desired color range by the filtering of white light; and 2) their use as conventional white light sources due to their potential for power-efficient, large area, high-efficiency light output. The objective of this thesis is to improve the efficiencies and lifetimes of white OLEDs using a novel co-evaporated 'hole-confining' structure. Generally, the mobility of holes is higher than the mobility of electrons in organic small molecules. This mismatch in the mobilities of the carriers might result in an imbalance in the number of holes and electrons in the emitting region, reducing the probability of their recombination and resultant light emission. In the first part of this thesis, we improve the efficiencies of a multi-layer, white light-emitting OLED by using a 'hole-confining' concept to improve the balance of carriers in the desired region and obtain a resultant increase in luminance and efficiencies. This is achieved by inserting a thin layer of hole blocking material before the emitting layers to form a 'hole-confining' structure to slow down the flow of fast moving holes and confine them in the emitting layers. In the second part of the thesis, we improve the lifetimes of these high-efficiency white OLEDs by using a 'co-evaporation' concept. We co-evaporate the thin hole-confining layer with another compatible material to stabilize the devices and improve their lifetimes to ultimately obtain efficient and stable white light-emitting OLEDs.