Effect of Precursor Solution on the Hydrothermal Synthesis of CQDs as Co-Sensitizers for Solar Cell Applications

Abstract

INTRODUCTION

A dye-sensitized solar cell (DSSC) is one of the latest trends in the production of green energy that uses organic dye to convert solar energy to electrical energy at a low cost. However, despite its advantages, the device has recorded the lowest power conversion efficiency (PCE) but holds one of the highest efficiency potentials among other photovoltaic cells. Hence, this project proposes a way to amplify the power generated by DSSCs by using an organic dye from Mayana leaves (Carolous blumei) and adding co-sensitizers, which help in widening of the absorbance range of a material, in the form of Carbon Quantum Dots (CQD) synthesized using Calamansi peels (Citrofortunella microcarpa).

METHODS

In this project, CQDs were made using 1.5 g of dried Calamansi peels and were hydrothermally synthesized in an autoclave for 1 hour with a.) 25mL of pure ethanol, and b.) 25mL of distilled water, respectively. It then underwent different characterization techniques such as Fluorescence Test, UV-Vis Spectrophotometer, and Particle Size Analysis to determine its properties. Lastly, these CQDs were added to the DSSCs containing organic dye from Mayana leaves to increase its voltage output.

RESULTS

The CQDs synthesized using water showed green coloration upon exposure to UV light and exhibited a maximum absorbance of 1.5 a.u. at 400 nm in the visible region of the UV-Visible spectrum whereas, CQDs synthesized using ethanol in the same process exhibited a yellow coloration and has recorded maximum absorbance of 2 a.u. at 400 nm with peaks of 545 nm, 605 nm and 670 nm as shown in the absorption spectrum of the UV-Visible region. In addition, particle size analysis (PSA) reveals quantum dots with an average size of ~1500 nm thus, confirming the successful synthesis of CQDs. Meanwhile, the extracted dye from Mayana leaves exhibited a maximum absorbance of 3.5 a.u at around 400 nm-which is inclusive to the range of wavelength needed to exhibit photovoltaic effect or the generation of voltage upon exposure to light.

DISCUSSIONS

Altogether, the 3 fabricated DSSCs containing no CQD, CQD-water solution, and CQD-ethanol solution were able to produce less than 10 mV, 19 mV, and 25 mV respectively in a multimeter. From these data, the researchers were able to successfully increase the power generated by DSSCs and greatly recommends the addition of CQDs as co-sensitizers to amplify its efficiency.