Targeted Grain-Boundary Regulation by Molecular Extrusion for Efficient and Stable n-i-p Perovskite Solar Cells

Although the power conversion efficiency (PCE) of perovskite solar cells (PSCs) has improved rapidly, nonradiative recombination at the perovskite/hole transport layer (HTL) interface, particularly in grain boundary regions, remains a key bottleneck in conventional n-i-p structured devices. In this work, p-Tolylphosphonic acid (p-TolylPA‌) is introduced as a bulk additive into the perovskite precursor solution. During crystallization, it selectively migrates and enriches at grain boundaries via a molecular extrusion effect, passivating defects and forming a dielectric shield, while simultaneously regulating crystal growth and alleviating residual stress. Femtosecond transient absorption spectroscopy further demonstrates that suppressing interfacial nonradiative recombination accelerates internal charge transport and enhances interfacial charge extraction efficiency. Meanwhile, the upward-shifted valence band maximum optimizes energy-level alignment, facilitating hole extraction. In addition, p-TolylPA clusters are hydrophobic, effectively blocking moisture and oxygen ingress. Consequently, this n-i-p PSC achieves a champion PCE of 25.58%; the encapsulated device retains over 90% of its initial efficiency after 1000 h of ambient storage and 500 h of continuous maximum power point tracking (MPPT).