PID Evaluation of Transparent Backsheet Modules

Abstract

This Work Deals with the Robustness of Transparent Backsheet Modules using Coating/PET/PVF (TPC) Polymer Layers when Exposed to an Extended Potential Induced Degradation (PID) Stress based on IEC 61215. Results show a Significant Power Decrease on the Front Side after 576h of Testing for Negative Voltage with Three Time more Impact at the Rear Side Despite the Absence of Glass. PID is Confirmed with Electroluminescence (EL) and Photoluminescence (PL). Measurements Showing the Appearance of Dark Areas on Several Cells and an Inhomogeneous Signal all Along the Module with “Light trails”. Moreover, Transmission Electron Microscopy Measurement Points out Sodium Presence at Both Cell Interface Despite POE Encapsulant and the Absence of Glass at the Rear Side. Two Types of PID Seem to be Present: Low Light Current-Voltage Measurements Suggest the Presence of PID-Potential at the Rear Side of the Cells And the Dark Area Could Be linked To PID-Corrosion Effect as Depassivation is observed with EL and PL.