Progress toward a stabilization and preconditioning protocol for polycrystalline thin-film photovoltaic modules

Cadmium telluride (CdTe) and copper indium gallium diselenide (CIGS) thin-film photovoltaic (PV) modules can exhibit substantial variation in measured performance depending on prior exposure history. We studied the metastable performance changes in these PV modules with the goal of establishing standard preconditioning or stabilization exposure procedures to mitigate measured variations prior to current-voltage (IV) measurements. We present the results of our case studies of module performance vs. exposure: light-soaked at 65°C, exposed in the dark under forward bias at 65°C; and finally longer-term outdoor exposure. We find that stabilization can be achieved using either light or dark bias methods. Additionally, we performed and present capacitance-voltage profile measurements on the modules to examine the changes in depletion widths or its hysteresis plus electronic carrier concentrations as a function of exposure.