A Facile Microwave-Assisted Synthesis of Carbon Dots and Their Application as Sensitizers in Nanocrystalline TiO2 Solar Cells

Carbon quantum dots (CQDs or CDs) recently have attracted attention due to their unique optical and chemical properties. Herein we demonstrate a facile protocol to synthesize CDs via the microwave-assisted method. In this research, we use citric acid as carbon source and urea as nitrogen source. The UV-vis absorption of CDs show two peaks at 326 and 408 nm respectively correspond to the π→π∗ transition of C=C bonds and n→π∗ transition of C=O or other bonds on the CDs surface. The CDs solution emit green color emission at wavelength 521 nm λexcitation = 365 nm), which the highest PL intensity is achieved by the CDs heated in microwave for 15 min. Moreover, we also conducted a preliminary study of the CDs as sensitizers in dye-sensitized solar cells (DSSCs) based on TiO2 nanocrystalline. The power conversion efficiency (η), fill factor (FF) and short-circuit current density (Jsc) of 0.29%, 0.31 and 0.36 mA/cm2, respectively, are achieved for the CDs based cell. This research suggests that the CDs have the potential application as sensitizers in DSSCs.