Nb/TiO2 oxides: A study of synthesis and electron transport mechanism as an ETL in a solar device

Abstract

Efficient solar devices to energy conversion are the key to a sustainable future. TiO2 dye solar cells are systems that present limited energy conversion efficiency due to recombination reactions. An alternative to reduce the back-electron recombination is the insertion of new oxides in electron transport material, such as Nb. However, what are the changes in electron lifetime and collection time caused by Nb insertion in TiO2 photoanodes? This work aims to analyze TiO2 dye solar devices with different Nb proportions synthesized by an easy and low-cost particle preparation methodology, Pechini. The techniques performed were X-ray Diffraction (XRD), Scanning Electronic Microscopy (SEM), and X-ray fluorescence to particle characterization. To the electrochemical analysis of the cells, j-V curves, Electrochemical Impedance Spectroscopy (EIS), charge extraction, Intensity Modulated Photovoltage Spectroscopy (IMVS), and Intensity-Modulated Photocurrent Spectroscopy (IMPS) were performed. The results showed a mix of anatase and rutile phase to TiO2 with Nb insertion and at the 5% of Nb proportion has been able to generate a cell with better electrochemical parameters (PCE = 5.43 %; j = 6.34 mA cm−2). The creation of energy substates below the conduction band has been able to increase the collection time (0.1748 s) and electron lifetime (0.15514 s) when compared to the cell with bare TiO2, suppressing the back-electron recombination but also difficulting the collection reaction.