Defect Investigation of Ti-Based Vacancy-Ordered Double Perovskite Solar Cell using SCAPS-1D

Despite the great promise of lead-based perovskite solar cells, their inherent toxicity and stability issues have hindered their practical applications in solar cells. Titanium(Ti)-based vacancy-ordered double perovskite Cs2TiBr6 was proposed as a non-toxic and stable substitute for lead-based perovskites. However, the efficiencies of the Cs2TiBr6 double perovskite solar cells currently have a maximum value of only 3.28%, which is still far below typical perovskite solar cells. Since the bulk defects inside the Cs2TiBr6 absorber layer are the main reason for degrading the performance of the Cs2TiBr6 double perovskite solar cell, it is worthwhile to investigate the bulk defect density in the absorber layer to optimize the performance of the Cs2TiBr6 double perovskite solar cell. In this work, we simulate the Cs2TiBr6 double perovskite solar cell with the FTO/SnO2/Cs2TiBr6/PEDOT:PSS/Au structure by using SCAPS-1D simulation software. We investigate the effect of the bulk defect density in the Cs2TiBr6 absorber layer for the performance of the Cs2TiBr6 double perovskite solar cell. The conclusion is that there is a threshold value for the bulk defect density in the Cs2TiBr6 double perovskite solar cell. Moreover, we obtain an optimal efficiency of 9.97% in the Cs2TiBr6 double perovskite solar cell by optimizing the bulk defect density. Our numerical simulation results show that the Cs2TiBr6 double perovskite solar cell has excellent potential and appropriate defect passivation is conducive for improving its performance.