Impact of A‐Site Cation Substitution on Electronic and Optical Properties of 0D Perovskite Derivatives A ₄ PbCl ₆ (A = Li, Na, K, Rb, Cs)

Zero‐dimensional (0D) perovskite derivatives A 4 PbCl 6 (A = Li, Na, K, Rb, Cs) are promising for optoelectronic applications due to their unique properties. However, synthesizing pure‐phase samples is challenging, and the impact of A‐site cation substitution remains less explored. Addressing these challenges, first‐principles calculations based on density functional theory (DFT) are employed to investigate the electronic and optical properties of A 4 PbCl 6 perovskite derivatives. The calculations reveal that the substitution of A‐site cations not only modifies the lattice parameters but also alters the distribution of the local electrostatic field within the crystal. These changes lead to variations in the electron density around the Cl and A atoms, thereby tuning the electronic structure and optical properties of the system. Specifically, Cs 4 PbCl 6 exhibits the highest extinction coefficient in the ultraviolet (UV) region, indicating enhanced optical activity, while K 4 PbCl 6 shows greater transparency due to its lower extinction coefficient. The results not only elucidate the impact of A‐site cation substitution on the properties of 0D perovskite derivatives but also provide essential theoretical insights for the rational design of new optoelectronic materials, particularly for UV detection and transparent applications.