Abstract:Cs2TiBr6, characterized as a lead-free vacancy-ordered double perovskite material, demonstrates notable stability and photoelectric performance, rendering it suitable for application in perovskite solar cells. However, the experimental efficiency of this material is currently limited, achieving only 3.12%. This efficiency limitation primarily stems from the material’s wide bandgap, which results in insufficient light absorption. To address this issue, this study utilized Cs2PtI6-xBrx for band structure fine-tuning. By adjusting the bandgap of Cs2PtI6-xBrx through Br- doping, not only was the alignment of the energy bandgap in the absorption layer effectively adjusted, but the cutoff range of light absorption was also significantly expanded. Setting the Cs2PtI6-xBrx bandgap to 1.4 eV resulted in optimal device performance. Additionally, comparative analyses aimed at boosting solar cell efficiency were performed on both hole transport and electron transport layer materials. Subsequently, the structure of the perovskite solar cell was optimized using an FTO/TiO2/Cs2TiBr6/Cs2PtI6-xBrx/Cu2O/Au configuration. Furthermore, the influence of the absorber layer thickness and defect density on device performance was studied. Ultimately, this configuration enabled the Cs2TiBr6/Cs2PtI6-xBrx solar cell to achieve a peak conversion efficiency of 29.69%.