Encapsulation technologies for thin-film photovoltaic devices
This project will develop a range of encapsulation materials and techniques for both polymer:fullerene and perovskite PV devices. A range of insulators (e.g. Al2O3 / ZrO2 / SiN / SiO2) and polymers (PS / PMMA / PET) will be explored for their barrier properties and their compatibility with the PV devices fabricated in our labs. These materials will be used both on their own, and in multilayer structures that are known to have enhanced barrier properties. Our aim is to develop and characterise a range of encapsulation strategies and combine these with our most stable polymer:fullerene and perovskite PV devices. Device operation will be tested under both accelerated aging conditions and at the Sheffield Solar Farm under real-word conditions. These measurements will be correlated with other studies on the water / oxygen ingress rate through encapsulation layers by monitoring the reduction in the optical density of an encapsulated calcium film, and by tracking changes in the PL emission intensity of the functional semiconductors. We will also utilise a number of analytical techniques used to explore the structure of the encapsulation films, including scanning electron microscopy (SEM) on device structures that have been cross-sectioned using a focused ion-beam, and ion-assisted X-ray photoelectron spectroscopy to probe through the encapsulation layers and explore chemical changes that occur at the electronic interfaces in the device as degradation proceeds.