N-doped Carbon Dots for Deep Blue emission and CD-LED device with 402 nm Electroluminescence

Abstract

Among the three primary colors, achieving the blue emissive organic light-emitting diodes is necessary as well as challenging at the same time. Deep blue light-emitting diodes (emission wavelength < 450 nm) are crucial for display and AR/VR applications. However, several factors limit the functionality of the blue OLED device. The higher photon energy coming from the recombination of holes and electrons degrades the organic emitters in blue OLEDs; to overcome this issue, researchers are moving towards low-dimensional nanomaterial-based devices. Among these materials, Carbon dots are easy to synthesize, cheap, and non-toxic, making them suitable for cost-effective and environmentally friendly materials for displays. Here we synthesise an easy-to-prepare nitrogen-doped carbon dot using the solvothermal method. 2-amino-5-bromo pyrazine was taken as a nitrogen dopant along with terephthalic acid in DMF to obtain deep blue emissive carbon dots with PLQY of 60%. Structural characterizations confirm the spherical shape of the carbon dots, and the electroluminescence measurements reveal the deepest blue emission maxima around 402 nm. Furthermore, the CD-LED device shows maximum luminescence of 824 cd/ m2, maximum current density of 534 mA/cm2 and an External quantum efficiency of 2.58%, with Commission Internationale d'Eclairage (CIE) coordinates of (0.15, 0.08). All these device parameters are better than most of the previously reported values. Hence, solution-processed pyrazine-based nitrogen-doped CDs prove to be an ideal candidate for low-cost and efficient blue LEDs.