Development of devices and materials for small molecular organic light-emitting diodes and hurdles for applications

Organic light-emitting diodes ( OLEDs ) are electrical driven devices which contain organic materials as emitting media. OLEDs have attracted attention widely in modern science and technology, due to their good features of high brightness, quick response, large viewing angle, simple manufacture process, and flexibility, etc. Currently, OLEDs have stridden forward to commercialization in its application field, such as flat panel display (FPD) and solid state lighting (SSL). Although small-size FPD products based on OLED have been in the markets, and prototype products in large dimensions also have come to true, there still exist challenges and hurdles. In this paper, we review the progress in OLED research of devices and materials, as well as OLED applications. Firstly, devices with different structures, such as host emitter based- and dopant emitter based devices, single-, double-, triple- and multilayer devices, as well as white OLED device are discussed, focusing on their working principles, corresponding device features and mechanism differences among them. Secondly, after introducing the strategies for OLED material research, different types of materials including hole transport materials, electron transport materials, various color emitters, and surface modification materials, are summarized, with their performance in OLED presented. Finally, the current challenges for applications are highlighted, and the focus of future research and development are proposed.