This work demonstrates the obtention of Nb2O5 nanoparticles by the microwave‐assisted hydrothermal synthesis method in a fast way and with the use of low temperatures. The heat treatment applied on the samples promotes the phase change in Nb2O5 from pseudohexagonal to orthorhombic as the temperature increases, with a particle size between 7.3 and 32.6 nm. The band gap of the samples decreases with increasing temperature, obtaining a minimum value of 3.04 eV at 800°C. Dye‐sensitized solar cells (DSSC) were assembled using the Doctor Blade coating technique. The photovoltaic parameters of open‐circuit voltage (Voc) and short‐circuit current density (Jsc) were evaluated. The cells showed a photovoltaic response, demonstrating that Nb2O5 has a semiconductive potential. The DSSC have different characteristics regarding Jsc and Voc, showing that according to the temperature increase in the semiconductor sample, there is a decrease in the photovoltaic parameters of the cells.

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The performance of niobium pentoxide (Nb 2 O 5 ) as photoanodes in dye-sensitized solar cells (DSSCs) and as catalysts in the photocatalytic degradation of Rhodamine B (RhB) was investigated. Four samples of Nb 2 O 5 (Nb 2 O 5 _SG, Nb 2 O 5 _CR, Nb 2 O 5 _PP, and Nb 2 O 5 _MA) were synthesized by four different methods, respectively, entailing the sol-gel, combustion, polymeric precursors, and a microwave-assisted hydrothermal reaction. In all these samples, the orthorhombic phase of Nb 2 O 5 was obtained, which resulted in different shapes and assemblies, which is very relevant because the surface area, shape, and size distribution of the nanoparticles significantly contribute to the optical process. The bandgap remained constant at 3.0 eV for all the samples, even for the sample prepared by the combustion method. An additional phase, which is related to local distortions, was revealed by Raman spectroscopy within the vibration range of 688-260 cm -1 . DSSCs using photoanodes with smaller and more dispersed Nb 2 O 5 particles showed better results than those with inhomogeneities. For comparison, DSSCs were assembled using two different counter electrodes, platinum and graphite. The DSSC with platinum showed better photovoltaic results, mainly with photocurrents from 1.17 mA.cm -2 for Nb 2 O 5 _CR to 1.64 mA.cm -2 for Nb 2 O 5 _SG. The same trend was observed for the photocatalytic degradation of RhB, where the smaller and dispersed particles of Nb 2 O 5 _CR and Nb 2 O 5 _SG exhibited the best performance and, respectively, degraded approximately 75% and 61% of the RhB dye over 180 min. Therefore, the results of this study established a correlation between the synthesis methods and photonic behavior.