A new optical modelling framework for photovoltaic devices

Abstract

There are a number of different modelling methods that can be used to simulate the optics of solar cells. However, solar cells and modules having both nanoscale and microscale features are difficult to simulate and therefore optimise using existing methods. The aim of this thesis was to investigate new methods of modelling such photovoltaic (PV) devices with advanced light-trapping structures and to accurately predict their system output under real operating conditions (i.e., local spectrum and varying angles of incidence). This objective was achieved through the development of a new optical modelling framework called the Angular Matrix Framework (AMF). The AMF allows the front and rear surfaces of a wafer-based solar cell to be modelled using different simulation methods. In this way, optical features with different scales with respect to those of the solar cell can be efficiently modelled separately. The angular responses of these features are then stored in matrices and can be combined to simulate the optical properties of the device. The effectiveness and accuracy of the method were verified by comparing AMF simulations with experimental results and simulation results obtained using established methods. Examples also showed that AMF could be used to optimise optical elements of various devices (e.g., back contact cells, passivated contact cells, silicon tandem cells and modules). To exemplify the utility of the AMF, a nanoscale anodic aluminium oxide (AAO)/metal light trapping heterostructure was simulated and optimised using Finite Domain Time Domain (FDTD) methods and AMF to determine the optimal pore size and spacing of the AAO template. In addition, the use of the AMF to accurately predict the PV power generation of a rooftop array in Brisbane, Australia was demonstrated with the difference between the actual and AMF-predicted generation being 1.30% compared with 1.66% for predictions using the established method PVWatts, the daily standard deviation also being reduced to 0.16 compared to 0.27 for the PVWatts calculations. These results highlight the potential to use the AMF to optimise cell and module components for system operation in different geographical regions and illumination conditions.