Accelerated Crystallization via Phase-Formation Promoters for Rapid-Annealed High-Efficiency Perovskite Solar Cells.

Two-dimensional (2D) perovskites, when integrated into formamidinium (FA)-based absorbers, offer a compelling pathway for passivating defects and enhancing the environmental durability of perovskite solar cells (PSCs). However, critical challenges remain in controlling crystallization during competing growths of low-dimensional and three-dimensional (3D) phases that determine ultimate photovoltaic performance. To achieve satisfactory crystal quality, energy-intensive, time-consuming annealing is commonly adopted, hindering scalable manufacturing. Herein, we unravel the crystallization kinetics and phase evolution of 3D-like domains within the 2D-confined framework of FA-based quasi-2D perovskites, and develop an NH4PbBr3-based phase additive (PA) for 2D perovskite synthesis to achieve high crystalline quality. The results demonstrate that the NH4PbBr3 PA preferentially promotes 3D-like crystallization and minimizes growth competition between low-dimensional components. The resultant 2D PSCs yield a record power conversion efficiency (PCE) exceeding 22% with impressive stability. Notably, we observe the evolution of an ordered 2D-to-3D-like gradient structure, enabling rapid formation of highly oriented, defect-passivated perovskite films under shortened annealing. Furthermore, we propose a comprehensive global evaluation index (CGEI) to assess the performance-processing balance of PSCs. The CGEI results confirm our strategy reduces energy consumption and material costs without compromising crystallization and device efficiency, thus providing an energy-saving, cost-effective route for scalable 2D PSC fabrication.