Study of Structure and Electronic Properties of Heterointerfaces for Photovoltaic Applications

The linkage between the atomic structure and the electronic property is complex for heterointerfaces involving multicomponent organic–inorganic systems because of large configurations and chemical possibilities. Understanding the structure–property relationship at the interface becomes further complicated with an asymmetric structure of organic molecules compared to the interface between planer solids. Here, we report on ab inito molecular dynamics (AIMD) simulations of the perovskite/PCBM ([6,6]-phenyl-C₆₁-butyric acid methyl ester) interface, where PCBM is an asymmetric molecule. Our AIMD calculations help us to navigate the vast number of possible atomic configurations of the interface. We have found that PCBM prefers to bind with the perovskite surface via an ester moiety over its fullerene moiety. The bonding at the interface and its stability are sensitive to the chemical composition at the perovskite surface, the PbI₂-terminated surface making a stronger binding ≈1 eV with PCBM, compared to the MAI-terminated surface. Later, we systematically studied the role of atomic defects on the perovskite surface and interface and linked it to interface stability and electronic properties.