Insight into Copper Doping Ratio on Optoelectronics Performance of Two-Dimensional Cu-Doped SnO₂ Nanosheets: an Experiment and DFT Study

The optoelectronics performances of two-dimensional Cu-doped SnO 2 nanosheets were investigated by first-principles calculations on the basis of density functional theory (DFT) and experiments. First, the crystal structures of Cu-doped SnO 2 were built and analyzed by using DFT within the generalized gradient approximation (GGA). The total energy of Cu-doped SnO 2 was discussed qualitatively and quantitatively from three aspects: charge density, band structure, and state density. The results show that copper doping has little effect on the charge density distribution because of the similar ionic radius of Cu 2+, Sn 4+, and the close bond lengths of Cu–O and Sn–O. The calculation results of band structure and state density show that the doping of a copper acceptor leads to the appearance of a new energy level at the top of the valence band and decreases the band gap of SnO 2 . With the guidance of theoretical calculation, the nanosheets of Cu-doped SnO 2 are constructed experimentally, and their optoelectronics performances are investigated. The experimental results exhibit that the Cu atom replaces the Sn atom in the SnO 2 lattice, while the Cu-doped SnO 2 retains the original rutile phase of the intrinsic SnO 2 . The sample with a doping ratio of 12.5% has more uniform particle morphology and dispersion characteristics. In addition, the 12.5% Cu-doped SnO 2 obtained the largest transient photocurrent of 3 μA/cm 2 and the lowest resistance to charge transfer, thereby indicating that the material has a remarkably higher optoelectronics performance under this ratio. The theoretical calculation and experimental results are consistent, which indicates that Cu doping effectively enhances the charge transfer in SnO 2 and enables it for high-quality application in optoelectronic catalysis.