Fundamental Mechanisms Behind the Reverse Characteristic of Cu(In,Ga)Se2 Solar Cells

Abstract

Partial shading of PV modules can lead to degradation of the shaded cells. The degradation originates from a reverse bias voltage over the shaded cells. In order to mitigate reverse bias damage in Cu(In,Ga)Se <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> (CIGS) modules, a good understanding of the fundamental mechanisms governing the reverse characteristic is required. In this study, a model is introduced that describes this behavior for CIGS cells. In this model, the low and non-Ohmic leakage current is accounted for by the space charge limited current component. A sharp increase in current that is typically observed in the CIGS reverse characteristics can be described by Fowler–Nordheim tunneling. This model has been validated against measurements performed at different temperatures and illumination intensities, and is able to describe the dependencies of the reverse bias behavior on both temperature and illumination.