Nitrogen-doped graphene quantum dots: Optical properties modification and photovoltaic applications

• Published in: Nano research Vol. 12; no. 5; pp. 1041 - 1047
• Main Authors: Hasan, Md Tanvir, Gonzalez-Rodriguez, Roberto, Ryan, Conor, Pota, Kristof, Green, Kayla, Coffer, Jeffery L., Naumov, Anton V.
• Format: Journal Article
• Language: English
• Published: Beijing Tsinghua University Press 01.05.2019; Springer Nature B.V
• Subjects: Atomic properties; Atomic structure; Atomic/Molecular Structure and Spectra; Biomedicine; Biotechnology; Chemistry and Materials Science; Condensed Matter Physics; Emissions control; Energy dispersive X ray spectroscopy; Fluorescence; Fourier transforms; Functional groups; Glucosamine; Graphene; Heat treatment; Immunoglobulins; Infrared spectrometers; Materials Science; Nanotechnology; Nitrogen; Optical properties; Oxygen; Oxygen atoms; Ozonation; Ozone; Photovoltaic cells; Photovoltaics; Quantum dots; Research Article; Solar cells; Weight; X-ray spectroscopy; optical properties; solar cells; nitrogen-doped graphene quantum dots; photovoltaics; ozone treatment
• ISSN: 1998-0124; 1998-0000
• DOI: 10.1007/s12274-019-2337-4

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 I D / I G 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.