New Encapsulant for PV Modules Designed for Recycle: A Lab Scale Prototype

Most of polymer families used today as encapsulants in PV modules are cross-linking polymers. This chemical reaction is an obstacle to their reuse after recycling process where a thermomechanical separation can supply encapsulant films to reuse them in new or repaired PV modules. In this document, we present the development of a dynamically cross-linked polymer resin (vitrimer) dedicated to PV applications. This material must necessarily possess properties essential to photovoltaic encapsulants such as good optical transmission and high thermomechanical properties to protect solar cells and maintain good adhesion between the different layers of a PV module. Simultaneously this vitrimer resin will make it easier to separate the various components of a PV module at its EoL (end of life), to improve recyclability and recovery of the various materials. First material level experimental campaign concerned the optical performance assessment and its positioning compared to commercially available products and enabled a first selection to upgrade the chosen formulations up to mono module size samples. Second material level test covered the adhesion testing where special samples had been obtained and tested at initial and after accelerated aging (1000 h DH). Both interfaces glass/encapsulant and encapsulant/backsheet were measured. These preliminary results showed an exceptional material performance that allowed us to process to module integration. This resin was successfully integrated into 2 ½-cell PV modules (200 x 200 mm) in glass-glass mono modules. These modules were tested at initial stage and then underwent to accelerated aging for 1000 h of damp heat exposure. Results showed a very good electrical performance for at least one of the three tested resins in mono-modules. The durability and recyclability of these PV modules with vitrimer encapsulant was demonstrated. These trials, which are very encouraging for further development, showed the main advantage of this new material namely its reusability as thermomechanical separation technics allow its recovery from the module and enables its reuse in a new photovoltaic module.