Fundamentals of solar cell physics revisited: Common pitfalls when reporting calculated and measured photocurrent density, open-circuit voltage, and efficiency of solar cells

Abstract

Very often, articles are found in the international literature reporting solar cells (single junction) with efficiencies above the Shockley-Queisser limit. In other similar papers, the short-circuit current density (Jsc) of solar cells are also reported with values that are above the maximum that a single absorber semiconductor can provide (without multiple-exciton generation), under the solar spectrum. For example, it will be easy to find both experimental and simulation reports for CdTe solar cells with Jsc values above 40 mA/cm2, under the AM1.5 solar spectrum. Unfortunately, in a pattern of perpetuating unsound analysis, recent articles with such parameter values cite old erroneous articles to justify their results. This fact reveals that some of the solar cell’s basic physics fundamentals have been forgotten or are not known by many researchers in the field. In this work, some of the solar cell physics basic concepts that establish limits for the efficiency, the short-circuit current density, the open-circuit voltage and even the fill factor for solar cells are reviewed. All these parameter limits will be shown as a function of the active semiconductor bandgap for single junction cells under the AM1.5 solar spectrum. Finally, it is explained what experimental and theoretical errors are typically made, causing the erroneous report of cell parameters, when the fundamental limits are not considered.