Relationship of recombination lifetime to dark current in silicon p-n junctions

Measurement of recombination and minority-carrier lifetimes has become a central activity in photovoltaic technology. The primary measurement techniques for silicon technologies are based on photoconductive decay (PCD) and microwave reflectance (mPCD). The measurement of the correct recombination lifetime depends on the carriers being confined to a given spatial region of a diagnostic structure. The electric field of the PN junction separates the charges, and the measured decay time does not represent the real minority-carrier lifetime. In these cases, the measured quantity is a function of the true lifetime and the sample structure. Here, we examine these effects, both experimentally and theoretically, for the n⁺-p device structure common to terrestrial photovoltaics.