Implementing Glucose-Derived Carbon Nanodots in Dye-Sensitized Solar Cells to Increase External Quantum Efficiency*

Although carbon nanodot isolation has been a consistent challenge due to the presence of molecular byproducts in a bottom-up synthesis approach using hydrothermal degradation of carbohydrate solutions, their resultant photoluminescence shows promise for down-converting UV photons into the visible regime with an associated increase in quantum efficiency. Excitation emission matrices show a wavelength-dependent luminescence with peak emission at 430nm for excitation at 340nm for carbon nanodot solutions, with a 90nm red shift in emission for devices. Carbonaceous nanodot solutions were derived from thermal treatment of high-concentration glucose solutions. Dialysis, combined with solid-phase extraction, of carbon nanodot solutions retained photoluminescent properties while successfully allowing for carbon nanodot isolation in acetonitrile, the dye solvent used for sensitizing the TiO₂ nanocrystalline matrix. Photoluminescence and external quantum efficiency of these carbon nanodot-modified devices are shown, including a nearly 800% increase in quantum efficiency at an excitation of 340nm, verifying this low-cost, earth-abundant approach to efficiency enhancement of dye-sensitized solar cells.