Solution-Based Synthesis of Ultrasmall Nb2O5 Nanoparticles for Functional Thin Films in Dye-Sensitized and Perovskite Solar Cells

Abstract A facile and new solution-based synthesis for the preparation of Nb 2 O 5 nanoparticles (NPs) is firstly introduced. Chain-like particles of 30 to 50 nm are synthesized through a hydrolysis reaction using an ethanol-based NbCl 5 precursor and H 2 O 2 as a strong oxidizer by UV treatment. A uniform dispersion of ultrasmall Nb 2 O 5 NPs with a quantum size of 2 to 5 nm is further obtained by modifying the procedure with acetic acid as a stabilizer. The resultant Nb 2 O 5 NPs are controllably coated on fluorine-doped tin oxide (FTO) conductive glass through 2-volt electrophoresis. The Nb 2 O 5 -coated thin film functioned as an effective blocking layer between a mesoporous TiO 2 and FTO; it thereby reduced the recombination at the TiO 2 /FTO/electrolyte interface in dye-sensitized solar cells. Furthermore, it serves as an ultrathin and compact hole blocking layer in perovskite solar cells, resulting in moderate hysteresis effect and improved photovoltaic efficiency from high-transmittance, low capacitance and low series resistance.