N-doped carbon dots for deep-blue emission and CD-LED device with 402 nm electroluminescence

Among the three primary colors, achieving the blue emissive organic light-emitting diodes is necessary as well as challenging. Deep-blue light-emitting diodes (emission wavelength < 450 nm) are crucial for display and AR/VR applications. However, several factors limit the functionality of blue OLED devices. 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, economical, and non-toxic; making them suitable as cost-effective and environment friendly materials for displays. Herein, we synthesize an easy-to-prepare nitrogen-doped carbon dot using the solvothermal method. 2-Amino-5-bromopyrazine is taken as a nitrogen dopant along with terephthalic acid in DMF to obtain deep-blue emissive carbon dots with a PLQY of 60%. Structural characterizations confirm the spherical shape of the carbon dots, and the electroluminescence measurements reveal the deep blue emission maxima around 402 nm. Furthermore, the CD-LED device shows a maximum luminance of 824 cd m^-2, a maximum current density of 534 mA cm^-2 and an external quantum efficiency of 2.58%, with Commission Internationale de l'Éclairage (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.