Zn–Porphyrin Antisolvent Engineering‐Enhanced Grain Boundary Passivation for High‐Performance Perovskite Solar Cell

Perovskite solar cells (PSCs) represent a promising and rapidly evolving technology in the field of photovoltaics due to their easy fabrication, low‐cost materials, and remarkable efficiency improvements over a relatively short period. However, the grain boundaries in the polycrystalline films exhibit a high density of defects, resulting in not only heightened reactivity to oxygen and water but also hampered charge transport and long‐term stability. Herein, an approach involving Zn‐porphyrin (Zn‐PP)‐upgraded antisolvent treatment to enhance the grain size and meanwhile passivate grain boundary defects in FA 0.95 MA 0.05 PbI 2.85 Br 0.15 perovskites is presented. The Zn‐PP molecules significantly improve structural and optical properties, effectively mitigating defects and promoting carrier transport at the perovskite/hole transport layer interface. The density functional theory simulation confirms that Zn‐PP forms a strong chemical bonding with the perovskite surface. With Zn‐PP passivation, the total density of state shifts to higher‐energy regions with molecular adsorption, especially near the valence and conduction band edges, indicating that there is an increase in conducting properties of the surface with molecular adsorption. The power conversion efficiency (PCE) of PSCs increases significantly as a result of this improvement, rising from 15.38% to 19.11%. Moreover, unencapsulated PSCs treated with Zn‐PP exhibit outstanding stability, retaining over 91% of their initial PCE.