Conventional and Inverted Light-Emitting Diodes with 386 nm Emission Wavelength Based on Metal-Free Carbon Dots

Ultraviolet (UV) light-emitting diodes (LEDs) are of great concern due to wide applications in the fields of solid-state displays, photocommunication, and scientific and medical instruments. During the past 10 years, organic and inorganic semiconductors have made great breakthroughs in short-wavelength emission. Nowadays, carbon dots (CDs), which possess distinctive superiorities of high stability, nontoxicity, and low cost, are promising all-band emission materials for the next generation of LEDs. However, the fabrication of CD-based LEDs (CD-LEDs) with emission wavelengths below 400 nm is still a huge limitation in this field. Herein, we prepared UV emission CDs with the photoluminescence emission wavelength of 371 nm. The UV-CDs are perfectly compatible with both conventional and inverted device structures so as to realize the currently shortest electroluminescent emission wavelength of 386 nm for CD-LEDs. The conventional UV-CD-LEDs possess the optimum luminance of 268 cd m-2 (5427 W sr-1 m-2) with an external quantum efficiency (EQE) of 1.115%. Meanwhile, the inverted UV-CD-LEDs possess the optimum luminance of 132 cd m-2 (2673 W sr-1 m-2) with an EQE of 0.869%. This work paves a new road to manufacture carbon nanomaterial-based UV emission devices with high luminance, EQE, and stability.