Interfacial and Electrical Properties of Si/APS/MAPbI₃ Heterostructure: An Ab Initio Study

In this study, we propose using 3-aminopropyl silane (APS) in the silicon/methylammonium lead iodide (MAPbI3) heterostructure to enhance interface properties. A first-principles study of the Si/APS/MAPbI3 heterostructure can provide a new approach to using this structure in advanced semiconductor devices. Using density functional theory and density-functional-based tight-binding methods, we investigated the electronic properties of the Si/APS/MAPbI3 heterostructure, including the density of states, band-edge orbitals, and electron deformation density. The effect of passivating compounds on the silicon surface has also been studied. The interface passivating structures used in this study include APS, OH molecules, and oxygen atoms, which are consistent with the experimental processes of APS attachment on the silicon surface. In such a structure, the amine group of the APS molecule acts as a cation in the perovskite structure, while the oxygen atoms of APS are bonded to the silicon substrate. In addition, other dangling bonds on the silicon surface are passivated by oxygen atoms and hydroxide molecules. The obtained results show that APS molecules can effectively passivate dangling interface bonds. However, the bonds on the surface of silicon change the Fermi energy (as an n-type semiconductor), and we have proposed a solution to control these changes. Our calculations show that the Fermi energy of the silicon surface can be more than 0.2 eV inside the conduction band. Also, the examination of band-edge orbitals shows that the effect of interfacial compounds on the formation of trap states is insignificant. The impressive optical properties of perovskite materials, together with the availability of silicon substrates, can provide significant progress in the development of low-cost and high-performance devices based on such structures.