Sol-Gel Synthesis of Copper Doped TiO2 Thin Films for Third Generation Solar Cells

Abstract

Dye-sensitized solar cells (DSSCs) have gained a great attention because they deliver good efficiency in power conversion, ease of manufacturing and lower costs, making them the most promising alternatives to traditional photovoltaic systems. DSSC photo-anodes were manufactured using nanostructures of undoped Titanium dioxide (TiO2) and Copper (Cu) doped TiO2 (CTO) in this study (2% and 4% concentration by wt. of Cu). The sol-gel process was utilized to synthesize these nanostructures. For materials analysis, Raman Spectroscopy, FTIR, UV-Visible (UV-Vis) spectrophotometer, EDS analysis, and scanning electron microscopy (SEM) were used to evaluate the material's properties, such as structural, optical, and morphological properties of prepared nanostructures. The FTIR spectra of three samples showed that intensity varied as we change the Cu concentration with TiO2. The peak intensity decreases in case of 2% and and 4% CTO. The Raman spectra of bare TiO2 and Cu doped TiO2 showed the shift in peaks, more intense peak is observed at 606cm-1 corresponding to A1g mode in TiO2. The lower peak is at 413cm-1 in case of 2% while in 4% CTO it is shifted to 404cm-1. SEM analysis revealed that doping of Cu with TiO2 increase the surface area of TiO2 nanoparticles and hence increase the conversion efficiency of cells. The average particle size of doped titania was observed about 60 nm. EDS analysis of the samples is done along with the SEM analysis to study the elemental composition of the samples. The EDS analysis of the bare andCu doped titania confirmed the synthesis of titania nanostructures and Cu doping. In UV-Visible analysis, the absorption improves with increasing Cu doping concentration, whereas the band gap decreases from 3.25 eV to 3.02 eV. The band gap value of undoped TiO2 is measured to be 3.25 eV, which was calculated using tauc plot. The band gap of 2% CTO was 3.17 eV, and of 4% CTO was measured as 3.02 eV. The solar cell device was fabricated, and solar simulations (J-V measurements) were performed, the photovoltaic parameters such as open circuit voltage (Voc), short circuit current density (Jsc), fill factor (FF) and efficiency (𝜂) were calculated. Simultaneous improvements in photovoltaic performance were achieved by Cu doping. In comparison with bare titania and 2% CTO, the 4% Cu doped TiO2 exhibits the higher efficiency (𝜂) of 1.76%.