Many basic texts already exist that describe the materials science aspects of solar cells and solar photovoltaic (PV) modules. The nomenclature used to describe solar cells in these texts is often difficult for the novice to understand and relate to basic concepts in optics. This tutorial text utilizes many of these materials science and solid-state physics texts as references, but it takes a slightly different approach. The goal herein is a description of the basic function of solar cells from an optical perspective. The fundamental principles of photovoltaic solar converters are examined with emphasis on their optical properties, and the requirements for the production and manufacturing of efficient and cost-effective light converters.
Rather than describing all the numerous specific examples of solar cells that include silicon (Si), copper indium diselenide (CuInSe 2), gallium arsenide (GaAs), and cadmium telluride (CdTe ), among others, the approach here is to give a broader view of what these devices actually have in common. In typical texts, the description of solar device performance is made in terms of Fermi statistics (e.g., of electrons). In these texts, doping and electron concentration profiles are described, as well as specific differences in solar cell geometries and methods of their construction discussed. In contrast, this text concentrates on describing solar cells using Boson statistics for photons. Although both approaches are outlined and presented, the emphasis is on the Planck equation rather than on the Fermi equation. In other words, we will view things from the standpoint of the photon rather than the electron. Hopefully, this distinction will allow the reader to understand the basics of solar cell-device design, as well as developments that will occur in the future. This text provides a background from which the reader may delve into other texts in order to gain a further practical understanding of solar cell-device structures. Throughout the text, general methods of solar cell testing and characterization are also outlined. The methodology in this text is by no means novel, and is a result of the work of many researchers who have shared the goal of understanding the fundamental limitations to conversion efficiency. These researchers agree that the performance of solar cells is determined by how a material absorbs, reflects, uses, and even emits light.
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