Detecting and Understanding Sodium Movement in Solar Panel Encapsulant Polymers

Published

October 28, 2020

Author(s)

Stephanie Moffitt

Abstract

Large, utility-scale solar farms currently represent the most cost-efficient form of solar panel installation. However, photovoltaic (PV) panels in large arrays operate at high voltages and as a result, can experience potential-induced degradation (PID). At these high voltages, leakage currents drive sodium out of the glass at the front of the panels, through the polymer encapsulant, and into the sensitive electronics at the core. Sodium migration through PV polymer encapsulants is linked to several types of PID. Initial work suggests that changing the polymeric encapsulant layer could limit sodium migration. However, the polymer characteristics and mechanisms which moderate sodium migration are not understood. In this work PV panel encapsulants will be investigated to understand how sodium moves through this polymeric layer. Glass/encapsulant coupons with an area of 35 cm2, mimicking the structure of full-sized panels, will be exposed to high voltages to evaluate degradation. Several coupon samples containing small PERC (passivated emitter and rear contact) cells will be periodically monitored via current versus voltage (I-V) measurements and electroluminescence imaging to track performance degradation. Coupon samples without cells will be made into cross sections for materials characterization. Cross-sectional analysis, using energy dispersive spectroscopy, will quantify the amount of sodium which has moved through different encapsulant polymers (ethylene-vinyl acetate (EVA), polyolefin, and ionomer). X-ray photoelectron spectroscopy will probe the chemical state of the sodium which has migrated into the polymeric layer. In tandem, the chemistry and structure of the polymers will be characterized to develop an understanding of which polymer characteristics limit sodium movement. Micro-Raman and micro-FTIR (Fourier transform infrared spectroscopy) will provide cross-sectional mapping of polymer chemistry and phase...

Proceedings Title

Proceedings of the 37th European Photovoltaic Solar Energy Conference and Exhibition

Conference Dates

September 7-11, 2020

Conference Location

Lisbon, PT

Conference Title

37th European Photovoltaic Solar Energy Conference and Exhibition

Pub Type

Conferences

Keywords

Degradation, Encapsulation, Interfaces, PV Module

Citation

Moffitt, S. (2020), Detecting and Understanding Sodium Movement in Solar Panel Encapsulant Polymers, Proceedings of the 37th European Photovoltaic Solar Energy Conference and Exhibition, Lisbon, PT (Accessed April 19, 2025)