First-Principles Study of Molecular Adsorption on Lead Iodide Perovskite Surface: A Case Study of Halogen Bond Passivation for Solar Cell Application

Organic molecules have recently been used to modify the surface/interface structures of lead halide perovskite solar cells to enhance device performance. Yet, the detailed interfacial structures and adsorption mechanism of the molecular modified perovskite surface remain elusive. This study presents a nanoscopic structural view on how organic molecules interact with the perovskite surface. We focus on the halogen bond passivated lead iodide perovskite surface, based on first-principles calculations. Our calculations show that organic molecules can interact with the perovskite surface via halogen bonds, which modifies the interfacial structures of the perovskite surface. We also constructed a detailed potential energy surface of the perovskite surface by moving the adsorbed molecule along different axes of the unit cell in order to comprehensively understand perovskite surface structures. This study demonstrates the effectiveness of modifying the perovskite surface structure via a molecular adsorption approach, and anticipates that the properties of perovskite materials can be further improved by a molecular engineering method.