Our ‘solar reliability’ area focuses primarily on studying the thermomechanical reliability of photovoltaic module components, from frontside optics to encapsulation and backsheet structures. We utilize a fracture mechanics based approach to understand the fundamental degradation mechanisms of module materials and interfaces. This includes significant participation from national laboratories and industry collaborators, who provide us with the most modern and relevant solar technologies.
Until now, a reliable and repeatable method of characterizing adhesive properties of module interfaces has not existed. However, through collaboration with the Bay Area Photovoltaic Consortium (BAPVC) and the National Renewable Energy Laboratory (NREL), we have developed simple metrologies that, for the first time ever, provide direct, quantitative measurements of adhesion in encapsulation and backsheet structures. These techniques have been used to evaluate adhesion in 30-year-old field modules and, ultimately, provide a framework for one-to-one comparisons of modules that have operated in different terrestrial environments.
Recent work on concentrating photovoltaics (CPV) has been carried out as part of the Department of Energy SunShot Initiative's PREDICTS program, and in collaboration with the NREL and major multijunction PV companies including Solar Junction and Boeing’s Spectrolab. Solar power generation with high-efficiency multijunction CPV cells has been an area of significant interest in recent years, as improved concentrator systems have enabled cost effective terrestrial deployment. While these systems have held a clear advantage in conversion efficiency over their traditional silicon counterparts, with efficiencies that have long exceeded 40% and have even recently reached as high as 46%, questions regarding long term reliability remain as availability of in-field exposure data is limited. Furthermore, environmental degradation is of greater concern as cells are subjected to higher incident flux of ultraviolet light and larger temperature cycles. From optics to encapsulation to the cells themselves, we have developed and employed testing methods to evaluate the reliability of these materials, and furthermore have developed predictive models to help lay groundwork for development of new materials in CPV.
Current Research Projects
- Tearing of Backsheet Structures in Photovoltaic Modules
- Thermomechanical Degradation of Multijunction Photovoltaics
- Developing New Testing Metrologies for Brittle Films and Fragile Substrates
- Reliability and Degradation of Optics and Encapsulants and Concentrated Photovoltaics
- Increasing Adhesion Energy of Organic/Inorganic Interface Through Nanoscale Structures
- Adhesion and Reliability of Photovoltaic Materials
- Adhesive Bonded Composite Joints
- Full-field Deformation Mapping
- Reliability and Enviornmental Degradation of Polymer-Oxide Interfaces