Síntese e caracterização de óxido de nióbio para aplicação fotovoltaica

Abstract

This work presents the synthesis and characterization of niobium pentoxide (Nb₂O₅) with potential application in photovoltaic devices, using ammonium niobium oxalate as a precursor and hydrogen peroxide as the oxidizing agent. Thermal precipitation routes (90 °C) and microwave-assisted hydrothermal treatment (120 °C/1h) were employed, followed by calcination at 550 °C and 600 °C. The innovation of this study lies in the simplicity and low cost of the method, which enabled the formation of the pseudo-hexagonal crystalline phase (TT-Nb₂O₅) at moderate temperatures, without the need for complex synthetic routes. Thermal analyses (TG/DSC) indicated thermal stability above 400 °C, with exothermic events associated with phase transition. X-ray diffraction (XRD) confirmed the formation of the TT-Nb₂O₅ phase with crystallite sizes around 24 nm. Spectroscopic techniques (Raman, FTIR, and UV-Vis) revealed characteristic vibrational bands of Nb–O and Nb=O bonds, as well as an optical band gap ranging from 3.78 to 4.02 eV, consistent with semiconductor materials. SEM and TEM images showed spherical, agglomerated, and nanoscale particles (<25 nm), while SAED analyses evidenced the evolution of crystallinity. Chemical composition assessed by EDS indicated high purity, with Nb and O contents close to stoichiometric values. The results demonstrate that the synthesized Nb₂O₅ exhibits structural, optical, and morphological properties suitable for use as an electron transport layer (ETL) or hole-blocking layer (HBL) in perovskite and dye-sensitized solar cells (DSSC), contributing to the development of high-efficiency, low-cost photovoltaic technologies.