Helium permeation as a fast quality indicator for barrier properties of solar cell encapsulates

The advent of flexible electronic devices and flexible thin-film photovoltaic modules increases the need for transparent and flexible high-barrier films. Conventional methods for measuring the barrier properties of such films are costly and time consuming. In our work, we present a method where we correlate water vapor and helium transmission rate measurements on strained barrier films with thin-film solar module performance. We show that the detected properties correlate well with the performance of a CIGS mini module exposed to damp-heat environment. The critical strain limit for a substantial decrease in barrier properties was identified for an ETFE-based barrier film incorporating an inorganic barrier layer. It was found that the detection of the helium transmission rate provides a fast and reliable way to identify damage to barrier films and is therefore suitable as means for quality control or incoming goods inspection.