A new and simple method for simulation of lattice mismatch on the optical properties of solar cells: A combination of DFT and FDTD simulations

Since controlling strain in different types of heterostructures devices causes the improvement of properties and functionalities in real devices, considering this matter is vital in simulation. In this paper, the impact of strain in the interface of different layers of solar cells has been investigated with density functional theory (DFT) and finite-difference time-domain (FDTD) techniques. We have simulated the complex issue of strain and relaxation of atomic layers by using a new, effective and simple method and using a precise meshing technique. The amplitude and region of the strain have been meshed to specific values. The lattice strain is included in both simple and gradient patterns in the theoretical simulations. The strain factor has been considered in two steps; between active layers in solar cells and between the active layer and the electron transport layer (ETL). DFT results indicate alterations in the structural and optical properties of the material as a function of strain. The results of DFT have been used in FDTD simulation. To describe this new method, we used perovskite as the active layer in the solar cell. We realized that the electric and optical parameters such as short circuit current density, absorptance, and reflectance of strained solar cells are different in comparison to strain free cells, and applying strain to the contacting layers in the solar cell alters the optoelectronic properties of the device.