Density Functional Theory Calculations of Photovoltaic Materials

Photovoltaic (PV) materials are gaining rapid popularity for their use in commercial solar cell applications. Due to the growing need for high efficiency solar cells, new materials such as perovskites are being researched. While the conventional experimental methods are still used to test new PV materials, PV modelling is gaining importance as an efficient and cheap alternative to physically synthesizing and testing each new material. In the PVMD group at TU Delft, multiple stages of modelling PV materials to study their efficiency have been researched, however, an ab initio method to obtain fundamental opticaland electrical properties of new materials is currently absent. While these properties are currently studied using experimentation, this thesis aims to provide a reliable simulation procedure to calculate the optical and electrical properties of PV materials using Density Functional Theory (DFT) softwareand verify its accuracy. The fundamentals of DFT and its implementation in DFT software are first studied to better understand the Vienna Ab Initio Simulation Package (VASP) software, on which simulations are performed during this thesis. The VASP software is a plane wave classical DFT software that employs the Projector Augmented Wave (PAW) method for electron structure calculations and has a wide range of electron density functionals available in its library making it a perfect fit to study optical and electrical properties of materials using DFT. Based on their success in previous computational research on material properties, the PBE and HSE06 electron density functionals are used in this thesis for simulations. A step-by-step procedure is then developed for simulations on the VASP software using both the PBE and HSE06 functionals detailing every step involved in the simulation, the inputs required at each step and the configuration of the input files at every step in order to obtain the density of states, band structure, band gap and complex refractive index for PV materials. Monocrystalline Silicon, a wellstudied PV material is then used as acase study to examine the accuracy of the developed procedure. The procedure is then employed to study new and promising solar cell materials such as inorganic halide perovskites and inorganic perovskites with mixed halides. Multiple simulations are performed to study the variation in the band gap and complex refractive index of inorganic perovskites as the composition of the halides is changed. Finally, the trends visible in the properties of the different perovskites are analyzed to better understand the usefulness of the VASP simulations. Finally, recommendations are provided for future research into the study of PV material properties using DFT software such as VASP.Electrical Engineering | Sustainable Energy Technolog