Color Emission Carbon Dots with Quench-ResixAstant Solid-State Fluorescence for Light-Emitting Diodes

Since carbon dots (CDs) were reported in 2004, they have been widely used in various fields due to their outstanding optical properties. However, most CDs are self-quenched due to the direct pi-pi interaction in the solid-state aggregation. This shortcoming limits the wide application of CDs, because numerous optoelectronic devices and sensors usually require photoluminescent materials in the solid state. Therefore, designing and preparing carbon dots with multicolor solid emission is necessary. Here, solid-state fluorescence (SSF) CDs were prepared via a one-step solvothermal method, using MA and APTES as raw materials. Through adjusting the ratio of raw materials, solid-state emitting CDs with green, yellow, and orange colors are obtained. The fluorescence spectrum ranges from 490-625 nm, and the QYs are 34.06%, 38.07%, and 20.37%, respectively. For prepared CDs, the main reason for the solid-state emission is that the Si-O, Si-C, and Si-N bonds generated during the formation process can prevent the pi-pi interaction between the graphitized cores. The red shift mechanism of solid and liquid fluorescence is attributed to the decrease in particle size and the increase in the degree of particle aggregation within the unit range. In addition, based on these excellent photoluminescence properties, we have prepared colored light-emitting diodes-the CIEs are (0.22, 0.41), (0.38, 0.47), and (0.50, 0.43) (Commission Internationale de l'Elcairage coordinate)-and solid-state emitting CDs/epoxy films with high transparency and stability.