Effects of palladium doping on structural, mechanical，and opto-electronic behavior of Cs2Pt1-xPdxBr6 double perovskites

Stability in structure and mechanical properties, along with an appropriate band structure, plays a pivotal role in enhancing the performance of the absorber layer materials in perovskite solar cells. In this study, we have employed first-principles calculations to explore the effects of palladium (Pd) doping on the structural, mechanical, and optoelectronic properties of Cs2PtBr6 perovskite. The aim is to explore and identify absorber layer materials for solar cells with superior physical characteristics. Results demonstrated that pristine and Pd4+ doped Cs2PtBr6 are mechanically and dynamically stable, and they all belong to ductile materials. Electronic structure calculations show that Pd4+doping can induce the transition of Cs2PtBr6 from an indirect bandgap to a direct bandgap. Concurrently, with the increase of Pd4+doping concentration, the bandgap decreases, which is beneficial for light absorption. Optical property analyses have also confirmed that with the increase in Pd4+ doping concentration, there is a significant improvement in the optical absorption of Cs2PtBr6 within the visible light range. Particularly, double perovskite Cs2Pt0.25Pd0.75Br6 and Cs2PdBr6 stand out as the best candidates for the solar cell absorption layer due to their close proximity to the ideal bandgap (∼1.5 eV) and strong light absorption coefficients (exceeding 105 cm−1). The findings contribute to the development of light absorption layer materials in perovskite solar cells.