@article{Hasan2019, 
author = {Md Tanvir Hasan and Roberto Gonzalez-Rodriguez and Conor Ryan and Kristof Pota and Kayla Green and Jeffery L. Coffer and Anton V. Naumov},
title = {Nitrogen-doped graphene quantum dots: Optical properties modification and photovoltaic applications},
year = {2019},
journal = {Nano Research},
volume = {12},
number = {5},
pages = {1041-1047},
keywords = {optical properties, solar cells, nitrogen-doped graphene quantum dots, ozone treatment, photovoltaics},
url = {https://www.sciopen.com/article/10.1007/s12274-019-2337-4},
doi = {10.1007/s12274-019-2337-4},
abstract = {In this work, we utilize a bottom-up approach to synthesize nitrogen self-doped graphene quantum dots (NGQDs) from a single glucosamine precursor via an eco-friendly microwave-assisted hydrothermal method. Structural and optical properties of as-produced NGQDs are further modified using controlled ozone treatment. Ozone-treated NGQDs (Oz-NGQDs) are reduced in size to 5.5 nm with clear changes in the lattice structure and ID/IG Raman ratios due to the introduction/alteration of oxygen-containing functional groups detected by Fourier-transform infrared (FTIR) spectrometer and further verified by energy dispersive X-ray spectroscopy (EDX) showing increased atomic/weight percentage of oxygen atoms. Along with structural modifications, GQDs experience decrease in ultraviolet–visible (UV–vis) absorption coupled with progressive enhancement of visible (up to 16 min treatment) and near-infrared (NIR) (up to 45 min treatment) fluorescence. This allows fine-tuning optical properties of NGQDs for solar cell applications yielding controlled emission increase, while controlled emission quenching was achieved by either blue laser or thermal treatment. Optimized Oz-NGQDs were further used to form a photoactive layer of solar cells with a maximum efficiency of 2.64% providing a 6-fold enhancement over untreated NGQD devices and a 3-fold increase in fill factor/current density. This study suggests simple routes to alter and optimize optical properties of scalably produced NGQDs to boost the photovoltaic performance of solar cells.}
}