Humidity-Induced electrical conduction in fluropolymer-based photovoltaic backsheets

Abstract

Understanding the charge transport phenomena in photovoltaic (PV) backsheets is an important step in studying their insulating properties and the related degradation in the field. Temperature and relative humidity (RH) are two environmental factors that have a significant impact on the insulating properties of backsheets. In this work, the charge transport in a commonly used backsheet with Polyethylene terephthalate (PET) as the core insulating layer is studied as a function of temperature and RH. DC conductivity of backsheet samples is considered as the transport parameter for the analysis. The conductivity pre-exponential factor (σ0) and the activation energy (Ea) in the Arrhenius equation follow the Meyer-Neldel relation in the measurement range studied. To the best of our knowledge, this is the first time the compensation effect in the DC conductivity of backsheets subjected to various temperature and RH conditions has been reported. The physical significance of Ea in the context of electronic conduction is explored, and the variation of σ0 and Ea with RH is explained by a percolation model.