A Comparative Study of Coprecipitation and Solvothermal Techniques for Synthesizing Pure and Cu-Doped SnO2 Nanoparticles

Tin oxide (SnO2), with its low resistivity properties and high transparency in the visible spectrum, makes it an attractive electron transfer layer (ETL) for use in perovskite solar cells. Here, we use two techniques, coprecipitation and solvothermal, to synthesize pure and 4% copper-doped SnO2. The X-ray diffraction patterns revealed that the films synthesized using both methods have a crystalline structure with a tetragonal arrangement. Furthermore, the lack of any secondary peaks indicated the absence of mixed tin oxide (Sn2O4) or copper oxide (CuO) components. Additionally, it demonstrated that adding a 4% Cu doping concentration reduced the crystal size in both methods. The optical results indicate adequate transmission in the central range of the visible spectrum. Calculations were performed to find the energy gap of pure SnO2 in both techniques to be 3.85 eV and 4.17 eV, respectively. When we doped SnO2 with 4% Cu, this band gap energy decreased to 3.75 eV and 3.9 eV. Furthermore, with 4% Cu doping, the particle size decreases, as demonstrated by FESEM. The EDX spectroscopy images revealed that the synthesized nanoparticles consisted of copper, oxygen, and tin. The analysis of functional groups using Fourier transform infrared (FTIR) spectra and the roughness analysis using AFM images showed a decrease in roughness from 46.1 nm to 12.3 nm in doped samples prepared by solvothermal synthesis, compared to those synthesized by the coprecipitation technique from 4.7 nm to 0.3 nm. We discovered that Cu plays an essential role in reducing nanocrystalline SnO2 particle sizes. In addition, the solvothermal technique is more impressive than coprecipitation in the synthesis of tin oxide nanostructure.