Built-in Electric Field in Quasi-2D CsPbI₃ Perovskites Using High-Polarized Zwitterionic Spacer for Enhanced Charge Separation/Transport

Two-dimensional (2D) halide perovskites are promising candidates for the fabrication of stable and high-efficiency solar cells. However, the low power conversion efficiency (PCE) of cell devices using 2D perovskites is attributed to reduced charge transport caused by poor organic barrier conductivity. In this study, we propose the use of a high-polarized organic zwitterionic spacer, p-aminobenzoic acid (PABA), to construct novel quasi-2D perovskite structures with enhanced self-driven charge separation and transfer. The NH3+ and COO– groups in PABA generate an aligned electric field, promoting carrier separation and aggregation on the opposite edges of the inorganic layer. This enables efficient in-plane transportation along the inorganic layer. Additionally, PABA intercalated quasi-2D perovskite exhibits improved stability compared with counterparts with diamine cation spacers due to the strong interaction between −COO– and inorganic layers. Our findings suggest that high-polarized organic zwitterionic spacers, with NH3+ and COO– functionality, hold promise for stable and efficient quasi-2D perovskite solar cells.