Temperature- controlled spectral tuning of fullcolor carbon dots and their strongly fluorescent solid- state polymer composites for light- emitting diodes

The development of full- color/ white carbon- dot- based light- emitting diodes ( LEDs) has been achieved, which show promising applications in full- color and flexible displays, backlights, and novel lighting sources. The gram- level synthesis of these full- color carbon dots ( CDs) from citric acid by controlling the temperature has been achieved. By increasing the temperature from 120 to 180 C, two, four, and six light- emitting CDs can be obtained, for which the emission wavelength shifts from 440 to 585 nm. This result reveals that temperature has a huge impact on the evolution of surface states, that is, increasing the temperature brings about enhanced surface functionalization and passivation, resulting in a red shift of the emission wavelength and enhancement of quantum yield. Then, full- color CDs/ polymer composite phosphors are fabricated for efficient phosphor- based LED devices with quench- resistant solid- state fluorescence. By regulating the proportion of various CDs/ polymer phosphors, white LEDs are realized with Commission Internationale de L'Eclairage coordinates of ( 0.32, 0.33) and a color rendering index of 82.7. The as- prepared CD- based full/ white color LEDs can prove to be promising candidates for alternative light sources.