First-Principles Study on the Stability and Electronic Properties of Dion–Jacobson Halide A′(MA)n−1BnX3n+1 Perovskites

Two-dimensional (2D) hybrid organic–inorganic perovskites have shown great application potential in solar cells and other optoelectronic devices. However, due to their wide band gap and limited stability, 2D perovskites can not be good candidates for solar cell application. To cover this gap, we propose a new system of the Dion–Jacobson (DJ) phase with divalent organic cations to obtain suitable band gaps and stronger stability. Based on first-principles calculation, we study the structure, stability, and electronic properties of a series of 2D DJ perovskites, which adopt the general formula A′A n –1 B n X 3 n +1 (A′ = 1,4-phenylenedimethanammonium (PDMA) or 1,4-bis (aminomethyl)cyclohexane (BAC) divalent organic cations, A = methylammonium (MA), B = Ge/Sn/Pb, X = Cl/Br/I, and n = 1–4). The structural stability and thermodynamic stability are analyzed through formation energy and ab initio molecular dynamics (AIMD). The results show that all A′(MA) n −1 B n X 3 n +1 exhibit strong stability compared with their three-dimensional (3D) homologous perovskites. Besides, the AIMD shows that the perovskites still have a high stability at 600 K. Compared to the aliphatic cation BAC, the aromatic diammonium organic cation PDMA contributes to the conduction band and gradually decreases with the increase in the number of layers. The band gap decreases with the increase in the number of layers n and gradually approaches the three-dimensional (3D) band gap. This theoretical study should provide a theoretical basis for finding solar cells with excellent band gaps and improving the stability of the equipment.