Stangl, R.; Leendertz, C.; Haschke, J.: Numerical Simulation of Solar Cells and Solar Cell Characterization Methods: the Open-Source on Demand Program AFORS-HET. In: Rugescu, R.D. [Ed.] : Solar Energy. InTech, 2010. - ISBN 978-953-307-052-0, p. 319-352
Within this chapter, the principles of numerical solar cell simulation are described, usingAFORS-HET (automat for simulation of heterostructures). AFORS-HET is a onedimensional numerical computer program for modelling multi layer homo- orheterojunction solar cells as well as some common solar cell characterization methods.Solar cell simulation subdivides into two parts: optical and electrical simulation. By opticalsimulation the local generation rate G(x, t) within the solar cell is calculated, that is thenumber of excess carriers (electrons and holes) that are created per second and per unitvolume at the time t at the position x within the solar cell due to light absorption.Depending on the optical model chosen for the simulation, effects like external or internalreflections, coherent superposition of the propagating light or light scattering at internalsurfaces can be considered. By electrical simulation the local electron and hole particledensities n(x, t), p(x, t) and the local electric potential ϕ (x, t) within the solar cell arecalculated, while the solar cell is operated under a specified condition (for example operatedunder open-circuit conditions or at a specified external cell voltage). From that, all otherinternal cell quantities, such like band diagrams, local recombination rates, local cellcurrents and local phase shifts can be calculated. In order to perform an electricalsimulation, (1) the local generation rate G(x, t) has to be specified, that is, an opticalsimulation has to be done, (2) the local recombination rate R(x, t) has to be explicitly statedin terms of the unknown variables n, p,ϕ , R(x, t) = f (n, p,ϕ ). This is a recombination modelhas to be chosen. Depending on the recombination model chosen for the simulation, effectslike direct band to band recombination (radiative recombination), indirect band to bandrecombination (Auger recombination) or recombination via defects (Shockley-Read-Hallrecombination, dangling-bond recombination) can be considered.