Abstract: The toxic element Pb in CsPbX₃ limits its widespread application in the field of solar cells. Doping with the metal element Pd to replace Pb is an effective approach to reduce its toxicity while also modulating its optoelectronic properties. This study employs first-principles computational methods to analyze the effects of Pd doping on CsPbX₃ (X=Cl, Br, I) in terms of crystal structure, band structure, density of states, and electron localization functions at varying concentrations and orientations. The findings reveal that when Pd is doped into the orthorhombic CsPbX₃ (X=Cl, Br, I), a negative formation energy is achieved, indicating the stability of the structure at room temperature. With the incorporation of Pd, the band edge flattens, the effective mass of charge carriers increases, and the bandgap value decreases. The doping in the <100> orientation has the most significant impact on reducing the bandgap value, and as the concentration of Pd doping increases, the bandgap value of the system continues to decrease. This is attributed to the increased electron localization due to the d-p hybridization effect between Pd and Pb and X. The stronger Pd-X and Pd-Pb bonding at the microscopic level forms local potential wells, enhancing the material's light absorption capacity and photovoltaic conversion efficiency. This results in a significant increase in the absorption coefficient for visible light with wavelengths greater than 600 nm, expanding the visible light absorption range of the doped material. Additionally, Pd doping reduces the Pb content, thereby decreasing the material's toxicity. These findings are instrumental for the design and fabrication of novel perovskite solar cells.

Key words: Pd doping, CsPbX₃, first-principles calculation, optoelectronic property, electronic structure, perovskite, solar cell