Feeling blue? Blue phosphors for OLEDs

Organic light emitting diodes (OLEDs) have drawn great attention in the past two (plus) decades. Ever since the influential and groundbreaking work by Tang and Van Slyke(1) OLEDs have been viewed as the next generation flat panel display (FPD) technology as they offer several advantages for self-emitting displays, such as a wide viewing angle (almost 180 degrees), a thin panel (< 2 mm), light weight, a fast response time (microseconds and less), bright emission, and high contrast. Moreover, they can be made on flexible substrates, and are thus highly versatile. In reality, OLEDs have already been incorporated into some commercial products, like MP3 players, mobile phones, digital cameras, PDAs, etc. The SONY XEL-1 was the world's first commercial OLED TV, featuring a 3 mm thick panel, as well as breathtaking image contrast, brightness, and color. Later on, LG announced the debut of a 31 '' prototype and planned to have a 55 '' TV on the production line in 2012, while Samsung introduced a 42 '' prototype in 2011. In addition to its main application in display technology, OLEDs are also used as a lighting source, namely, as white-emitting OLEDs, or WOLEDs(2). For lighting purposes, WOLEDs have to meet stringent requirements. To compete with the fluorescent tube as a lighting source, a power efficiency of > 70 lm/W is preferred and the lifetime must be at least 10 000 h @ 1000 cd/m(2), with a color rendering index (CRI) greater than 80 %. For the OLED display, it is expected that the turning point will be around 2014 when the yield rate of production is expected to be greater than 70 %. The consequent cost-effectiveness, brightness, and portability of the OLED will represent a major threat to LCD products(3).