Metastability in Dark Current Diode Characteristics of Chalcogenide Photovoltaic Modules

Abstract

While present trends in commercial photovoltaic (PV) are set on a‐Si/c‐Si heterojunctions and promising perovskites, the chalcogenides still attract interest as an excellent candidate for coming multi‐ and heterojunction devices with perovskites. Continuously enhanced over the years, typical metastabilities in thin‐film devices still cause issues under outdoor operation. Unfortunately, qualitative assessment in commercial PV is solely focused on data at the maximum power point of its operation, whether in simple on‐site PV plant monitoring or following latest standards for certified laboratory testing, thus metastabilities merely register as undefined power fluctuations. Herein, it is shown that dark current characteristics are a simple and yet field‐fit method, to identify metastable changes and take suitable counter measures. With this study, using commercial CdTe and CIGS showcase modules of various manufacturers and production generations, it is demonstrated how dark current characteristics allow to pinpoint physical changes of the individual module, between its pristine state, outdoor operation, dark degradation, and stabilization, like a fingerprint. Using the two‐diode model, it is shown that alterations to respective regimes of the characteristic can be assigned to typical defects, defining the module's current state, and be used to it as a guide to evaluate its recuperation via preconditioning treatments.