Structural Engineering toward High Monochromaticity of Carbon Dots-Based Light-Emitting Diodes

Monochromaticity for light-emitting diodes (LEDs) is an important parameter. However, carbon dots-based light-emitting diodes (CDs-LEDs) usually suffer from broad emission, which limits the development of this material. In this work, high-quality carbon dots (CDs) with a quantum yield of 16.2% were synthesized. When they were mixed with poly(N-vinyl carbazole) (PVK) to form a homogeneous film, the solid-state fluorescence of CDs was realized. After fabrication and systematic optimization of the device, the full width at half-maximum (fwhm) of EL spectra could be narrowed to 64 nm in comparison with the fwhm of 77 nm for PL, demonstrating that structural engineering is an effective approach for improving the color purity of CDs-LEDs. Meanwhile, the performance of the devices is improving. The obtained CDs-LEDs display high monochromaticity with a maximum luminance of 681 cd/m2. This work provides a new way to optimize the monochromaticity and performance of CDs-LEDs.