Oxygen-Containing Diamine Cations Enable Highly Efficient and Stable 2D Dion-Jacobson Perovskite Solar Cells

Two-dimensional (2D) Dion–Jacobson (DJ) perovskites have been extensively investigated in perovskite solar cells (PSCs) owing to their superior stability and structural diversity. However, the efficiency is still limited by dielectric confinement and carrier localization in the transport process. Here, we introduced a new spacer cation, namely, 2,2′-oxybis(ethylamine) hydroiodide (OBEAI), which clearly clarified the fundamental physical properties of constructing 2D DJ perovskites to optimize charge transfer properties for high-performance 2D DJ PSCs. The strong electronegativity of OBEA enhanced the overlap of charge density in the spacing through its interaction with inorganic [PbI 6 ] 4– layers, promoting charge migration across confinement layers. In addition, the aggregation of strong electronegativity of OBEA and metal cations in precursor solutions enlarged the particle size, which reduced random nucleation sites, thereby inhibiting the production of low n -value perovskites ( n ≤ 2). Thanks to these merits, the electrons’ transport of (OBEA)MA 4 Pb 5 I 16 (MA: methylamine) was greatly promoted, which supported efficient charge extraction at the device level. The resultant (OBEA)MA 4 Pb 5 I 16 solar cells delivered a power conversion efficiency (PCE) of 14.33% and further improved to 18.81% based on (OBEA)FA 4 Pb 5 I 16 (FA: formamidine) with exceptional stability of T 90 (preserve 90% of the initial PCE) after 2000 h.