Optoelectric Properties of Doped Carbon Dot Nanostructures

Abstract

Carbon dots (C-Dots) can be defined as spherical-like carbon particles (graphitic fragments) with sizes less than 10 nm. Typically, C-Dots exhibit ample room temperature photoluminescence (PL) whereby the PL properties of C-Dots with a well-defined crystalline core is related to the size or conjugated domains of C-Dots accompany with contribution from the surface state, conjugated core, molecular configuration, and so on. However, up to date the exact mechanism of the PL origins of C-Dots depends on synthesis path and remains unsettled [1-3]. In this contribution we will discusses the synthesis, characterization and origins of PL properties of doped C-Dots their potential for applications as absorbers in solar cells. We discuss to use nitrogen doped C-Dots as active absorbing layer in a solar cell and how the electrical, optical, and chemical properties can be engineered by doping. We demonstrate that the doping can be efficiently used to modify the band structure of the C-Dots and meet the requirements for application in solar cells. To rationalize the measured experimental data, we also calculated using DFT in the sTDA approximation the absorbance spectra of pristine and nitrogen doped C-Dots. For computationally feasibility the diameter, d = 2.3 nm, of the C-Dots is chosen to be at the lower end of experimentally observed size distribution and the C-Dots consist of 3 carbon layers. Subsequently, these C-Dots have potential to be used as an absorbing material in next-generation solar cells for high energy photons to be absorbed by a lower bandgap transporter.