A methodology for experimentally based determination of gap shrinkage and effective lifetimes in the emitter and base of p-n junction solar cells and other p-n junction devices

An experimentally based methodology is described that determines the effective gap shrinkage and lifetime in the emitter of a p-n junction solar cell. It provides the first experimental means available for assessing the importance of gap shrinkage relative to that of large recombination rates in the highly doped emitter. As an additional result of the procedures employed, the base lifetime is also determined. The methodology pertains to a solar cell after the junction is formed. Hence each material parameter determined includes the effects of the processing used in junction fabrication. The methodology consists of strategy and procedures for designing experiments and interpreting data consistently with the physical mechanisms governing device behavior. This careful linking to the device physics uncovers the material parameters concealed in the data. To illustrate the procedures, they are applied to an n⁺-p solar cell having substrate resistivity of about 0.1 Ω cm.