Abstract
In recent years, computer simulation has become a standard tool for analyzing solar energy systems. The interaction of light with nanoscale matter can provide greater functionality for photonic devices and render unique information about their structural and dynamical properties. As the field of nanophotonics continues to experience phenomenal growth at both the fundamental research and applications level, computational modeling is essential both for interpreting experiments and for suggesting new directions – for example, in designing of thin-film photovoltaic cells. The demand for computer simulation continues to increase as researchers and developers tackle the tough challenges of designing new generation devices and optimizing current generation devices. This chapter is devoted to the development and application of the Finite-Difference Time-Domain (FDTD) method to solar energy systems. In addition, new models covering the latest advances in nanophotonics technologies, as well as key improvements to the numeric solvers and new usability features, are introduced in this chapter.
TopFinite Difference Time Domain (Fdtd) Method
The FDTD method numerically solves Maxwell’s curl equations by representing time and spatial derivatives as finite differences. The basic Maxwell’s curl equations in a three dimensional (3D) domain are expressed as (Taflove & Hagness, 2000):
(1) (2) where both the electric field
and magnetic field
describe the interaction between light and the solar cell. The solar cell is described by its permittivity
and permeability
. The parameters,
and
describe the optical properties of the solar cell. Expanding the curl operator in (1) and (2) and equating their respective vector components on each side appropriately, these equations can be represented with the following six equations in a Cartesian coordinate system (
x, y, z):
(3) (4) (5) (6) (7) (8) Key Terms in this Chapter
Solar Cell Efficiency: Is the percentage of electric power converted from incident light
Nanophotonics: Is the science and engineering of light–matter interactions that take place on wavelength and subwavelength scales where the physical, chemical or structural nature of natural or artificial nanostructured matter controls the interactions
Perfectly Matched Layer (PML): Is an artificial absorbing layer for wave equations with an absorbing material is that it is designed so that waves incident upon the PML from a non-PML medium do not reflect at the interface
Total-Field/Scattered-Field (TF/SF) Formulation: Is a method for injecting energy into the FDTD simulation.
Transparent Conductive Oxide (TCO): Is doped metal oxide used in optoelectronic devices such as flat panel display and photovoltaic.
Thin-Film Solar Cell: Is a solar cell that is made by depositing one or more thin film of photovoltaic material on a substrate.
Absorbing Boundary Conditions (ABCs): Are artificial absorbing layer for wave equations, commonly used to truncate computational regions in FDTD method to simulate problems with open boundaries.
Yee Cell: Is rectangular unit cells of a Cartesian computational grid so that each E-field vector component is located midway between a pair of H-field vector components, and conversely.
Finite Difference Time Domain (FDTD) Method: Is a powerful tool to solve electromagnetic problems based on the numerical solution of Maxwell’s equations
Courant Criterion: Is a necessary condition for convergence while solving Maxwell’s differential equations numerically.