(271d) Understanding Charge Transport in Polymeric Encapsulants Enables High Performance, Durable Photovoltaic Devices

Potential Induced Degradation (PID) is a class of degradation mechanisms in photovoltaic (PV) modules associated with the transfer of charge through the polymeric encapsulant layer. Initially identified in the 1980s, minimal progress in understanding PID was made until the growth of the PV industry in the 2010s, when transport of sodium ions in particular was identified as a critical factor in the most commonly observed form of PID. Because the phenomenon had long been associated with gross charge transport rather than transport of a specific species, standards and other design principles in the industry suggested that the volume resistivity of the encapsulant was the critical factor in preventing PID. However, this consensus overlooked the fact that ionic species may have different relative permeabilities across encapsulant material classes, hindering optimal material selection. In collaboration with the National Renewable Energy Lab, a series of studies was conducted to better understand the fundamental encapsulant material properties that contribute to mitigation or prevention of PID. This presentation will discuss these studies and their results, which have led to a broader understanding of the physics of charge transport in polymeric encapsulant materials and their relation to PV device performance.