Role of surface states on luminescence shift of caramelised sugar carbon dots for color conversion emitting devices
Isnaeni, B S Zufara, I W L Lewa, Y Herbani and M Shiddiq
Carbon dots made of various sources have shown unique and excellent optical properties for many potential applications, including light emitting devices. The luminescence origin of carbon dots is crucial in colour conversion emitting device applications. In this work, an intensive study on surface state effects of caramelised sugar carbon dots for colour conversion applications was done. Using caramelised carbon dots synthesised by microwave-assisted technique, we studied optical properties of carbon dots using photoluminescence, time resolved photoluminescence, Fourier-transform infrared spectroscopies, absorbance spectroscopy and Raman spectroscopy. We found that different concentrations of caramelised sugar dissolved in water caused absorbance and emission peak shift of carbon dots. However, life-time, crystal structure and functional groups of carbon dots were not significantly affected by carbon dot concentration. We have utilised this shifting luminescence effect in colour conversion light emitting devices using blue and green light emitting diodes. Caramelised sugar carbon dots, which were placed on top of light emitting diodes, were able to generate new colours. This work is useful for developing advanced lighting devices using carbon dots.