We have developed a high efficiency and deep blue organic light-emitting diodes (OLEDs) incorporating a 4-hydroxy-8-methyl-1,5-naphthyridine aluminum chelate (AlmND<sub>3</sub>) as the emitter and electron transporting layer (ETL). The blue AlmND<sub>3</sub> emitter, with an electron withdrawing group added to the well-known green fluorophore tris(8-hydroxyquinolinato)aluminum (Alq<sub>3</sub>), exhibited ambipolar charge transport as well as high electron and hole mobilities on the order of 10<sup>-5</sup> cm<sup>2</sup>/V·s, as deduced time-of-flight measurements. The magnitude of the electron mobility was 10 times greater than that of the widely used Alq<sub>3</sub> ETL, resulting in efficient charge balance in the AlmND<sub>3</sub> device. Based on a simple configuration of double heterojunction device, a blue device with the maximum external quantum efficiency of 1.58% and Commission Internationale de l'Eclairage (CIE) coordinates of (0.16, 0.08) was achieved at a brightness of 200 cd/m<sup>2</sup>. This study has revealed the fundamental nature of charge transport in hydroxynaphthyridine metal chelate and shed a new light on the design of high performance blue OLEDs.
© 2011 IEEE
Chih-Chien Lee, Chih-Hsien Yuan, Shun-Wei Liu, and Yih-Shiun Shih, "Efficient Deep Blue Organic Light-Emitting Diodes Based on Wide Band Gap 4-Hydroxy-8-Methyl-1.5-Naphthyridine Aluminum Chelate as Emitting and Electron Transporting Layer," J. Display Technol. 7, 454-458 (2011)