An Efficient Red Organic Light-Emitting Diode Using DCJTB Type Emitters Based on Silicone-Containing Julolidine Derivatives

Abstract

This paper reports the synthesis and electroluminescent properties of new red fluorescent materials, 4-(dicyanomethylene)-2-(1,1-dimethyl-7-trimethylsiliyl methyl-julolidyl-9-enyl)-6-(4-pentylbicyclo[2.2.2]octan-1-yl)-4H-pyran (DCJTMS) and 4-(dicyanomethylene)-2-(1,7-bistrimethylsiliylmethyl-julolidyl-9-enyl)-6-(4-pentylbicyclo[2.2.2]octan-1-yl)-4H-pyran (DCJDTMS). In these red emitters, the bulky groups such as trimethylsilane and n-pentyl-bicyclo[2,2,2]octane were introduced into and 4-(dicyanomethylene)-2-methyl-6-[p-(dimethylamino)-styryl]-4H-pyran (DCM) skeleton to increase the steric hindrance between the red emitters and prevent concentration quenching. An OLED device using 4-(dicyanomethylene)-2-(1,7-bis(trimethylsiliylmethyl)-julolidyl-9-enyl)-6-(4-pentylbicyclo[2.2.2]octan-1-yl)-4H-pyran (DCJDTMS) as a dopant exhibited the efficient red emission with a Luminous efficiency, Power efficiency and Commision Internationale De L’Eclairage (CIE_x,y) coordinates of 3.66 cd/A, 2.13 lm/W at 20 mA/cm² and (0.62, 0.38) at 7.0 V, respectively. Compared to device using 4-(dicyanomethylene)-2-(1,1,7,7-tetra-methyljulolidyl-9-enyl)-6-tert-butyl-4H-pyran (DCJTB), the red device using DCJDTMS showed the greatly improved EL efficiency due to the more bulky substituents of compound DCJDTMS.

Keywords:

• OLED
• Red fluorescence
• Trimethylsiliyl group
• n-Pentyl-bicyclo[2,2,2]octane
• DCJTB derivatives