In Situ Formation of Guanidinium Derivative and 2D/3D Heterostructure for 26.49% Efficient and Stable Inverted Perovskite Solar Cells

Inverted perovskite solar cells (IPSCs) face challenges in achieving both high efficiency and stability due to defects that induce non-radiative recombination. Here, we introduce 1H-1,2,4-triazole-1-ammonium chloride (HTA) as a multifunctional additive that reacts with formamidinium iodide (FAI) to generate a multi-amino guanidinium derivative. This in situ formed compound enables dual passivation by coordinating with Pb²⁺ ions and forming hydrogen bonds with I^- ions, while simultaneously templating a 2D/3D heterostructure. HTA effectively regulates nucleation kinetics, reduces defect density, and optimizes energy-level alignment. Consequently, the HTA-treated device achieves a champion power conversion efficiency (PCE) of 26.49% (certified 26.20%) with significantly enhanced stability. The unencapsulated device retains 89.15% of its initial efficiency after 2000 h in ambient air, and the encapsulated device maintains 95% of its initial PCE after 1000 h of maximum power point tracking. This strategy provides a promising route for developing high-performance and stable IPSCs.