Perspective on Host Materials for Thermally Activated Delayed Fluorescence Organic Light Emitting Diodes

Organic light emitting diode (OLED) is a new yet promising technology that is anticipated to replace the liquid crystal display technology in the very near future. The development of both the emitter and host materials for OLEDs is indispensable to realize high device efficiency and optimal performance. Though the presently commercialized OLED panels mostly utilize phosphorescence emitters, the all-organic thermally activated delayed fluorescence (TADF) emitting materials have some obvious advantages. Considerable progress has been made in search of better performing TADF OLEDs in the past few years. Although major research attention has been drawn toward reporting new TADF emitters, the hosts are equally important in TADF OLEDs, as the doped films of the emitters mostly yield better results than the nondoped films. There are already some good reviews on the TADF emitters in literature. In this review article, the literature data specifically aimed at hosting TADF dopants are carefully selected and comprehensively summarized and categorized into several sub-groups based on their structural features to draw the attention of the organic electronics research community toward developing new host materials for TADF OLEDs.