Milling Processing, Morphology, and Optical Characterization of Powders from Natural Pigments as a Potential Sensitizing Material for Optical Sensors and Dye-Sensitized Solar Cells

Abstract

Dye-Sensitized Solar Cells (DSSC) and optical fiber-based-sensors sensitized with organic dyes play a fundamental role in modern technology, particularly in the family of photovoltaic power generation devices and measurement of chemical variables. DSSC is low-cost, highly efficient, and easy to manufacture. Therefore, they are a suitable option for many engineering applications. This paper deals with natural pigment extraction (spirulina, carrots (beta-carotene), and beetroot) at different milling and temperature conditions. Nanoparticles were fabricated using an SPEX mill and a planetary ball mill. The particle size distribution, absorbance (UV-Vis), and powder morphology were obtained using Field Emission Scanning Electron Microscopy (FESEM). Herein, the optical characterization of modified TiO₂ powder at different temperatures and milling conditions is performed. Results indicate that each natural dye is sensitive to operational temperature. In addition, the absorbance of the pigments is affected by milling conditions and particle size distribution. During SEM characterization, rounded particles were observed in the starting materials with average sizes of more than 15 microns in diameter until they were reduced to nanometer ranges close to 100 using SPEX milling. The observed absorption spectra range from 400 nm to 642 nm for spirulina. Moreover, the experimental results show that the intensity of the absorption peaks is affected by the temperature, which indicates a degradation of the dye. Therefore, different combinations of natural dyes will be feasible to improve the wide range of light absorption of the visible spectra and stability of DSSCs and optical fiber-based sensors.