Fluorescent Carbon Quantum Dots Incorporated into Dye-Sensitized TiO2 Photoanodes with Dual Contributions

Fluorescent carbon quantum dots (CQDs) were prepared through bottom-up synthesis, which possess excitation wavelength-dependent photoluminescence properties upon excitation by near visible light. For the first time, CQDs were incorporated into N719-sensitized TiO2 photoelectrodes as the electron-transport medium, presenting dual contributions to the photo-to-electrical energy conversion: 1) spectral response compensation for the dye-sensitized TiO2 film at around 400 nm was successfully observed in the incident photon-to-current conversion measurements; and 2) intensity modulated photocurrent/photovoltage spectroscopy showed that the electron transport time, charge collection efficiency, and electron diffusion length in the TiO2 electrode were all improved after CQDs incorporation. An example of using the CQDs- containing photoanode in a solar cell device resulted in enhancements of 32 % and 21 % for the short-circuit current density and photo-to-electrical conversion efficiency, respectively.