Program
Electrical and Computer Engineering
College
Engineering
Student Level
Doctoral
Start Date
7-11-2019 2:00 PM
End Date
7-11-2019 3:45 PM
Abstract
With the continued advancements in the solar industry, the cost of solar electricity is quickly reaching parity with fossil-fuel-based generation. The movement toward transitioning to carbon neutrality as a state and as a country, has increasingly become a pressing issue as we begin facing a climate change crisis. One of the ways to continue to lower costs further is to reduce the degradation rate of solar modules and extend their lifetime well beyond the typical 25-30 years. The extended module lifetime in turn can positively influence the financial model and the bankability of utility-scale PV projects. Today, the highest-risk-priority solar module degradation mechanism is what is known as hot spots, often induced by cell cracks. In order to address this degradation mechanism, we make use of low-cost, multi-walled carbon nanotubes embedded in commercial screen-printable silver pastes, also known as metal matrix composites. When the carbon nanotubes are properly functionalized and appropriately incorporated into commercial silver pastes, the resulting metal contacts on solar cells show exceptional fracture toughness. The improved composite metal contacts possess increased ductility, electrical gap-bridging capability up to 70 µm, and "self-healing" to regain electrical continuity even after cycles of complete electrical failure under extreme strain. To further understand the mechanisms behind the resilient metal composites, in-situ strain experiments done under SEM were completed to get physical evidence of CNT bridging. The CNT metal composites have shown exceptional print quality, resulting in cell performance similar to the commercial paste. Accelerated thermal cycling tests on mini-modules constructed from aluminum back surface field (Al-BSF) cells show a slower degradation rate for the cells integrated with the composite grid fingers and busbars for the front surface metallization compared to the cells with conventional metallization.
Title: Low-Cost, Advanced Metallization to Mitigate Cell-Crack-Induced Degradation
With the continued advancements in the solar industry, the cost of solar electricity is quickly reaching parity with fossil-fuel-based generation. The movement toward transitioning to carbon neutrality as a state and as a country, has increasingly become a pressing issue as we begin facing a climate change crisis. One of the ways to continue to lower costs further is to reduce the degradation rate of solar modules and extend their lifetime well beyond the typical 25-30 years. The extended module lifetime in turn can positively influence the financial model and the bankability of utility-scale PV projects. Today, the highest-risk-priority solar module degradation mechanism is what is known as hot spots, often induced by cell cracks. In order to address this degradation mechanism, we make use of low-cost, multi-walled carbon nanotubes embedded in commercial screen-printable silver pastes, also known as metal matrix composites. When the carbon nanotubes are properly functionalized and appropriately incorporated into commercial silver pastes, the resulting metal contacts on solar cells show exceptional fracture toughness. The improved composite metal contacts possess increased ductility, electrical gap-bridging capability up to 70 µm, and "self-healing" to regain electrical continuity even after cycles of complete electrical failure under extreme strain. To further understand the mechanisms behind the resilient metal composites, in-situ strain experiments done under SEM were completed to get physical evidence of CNT bridging. The CNT metal composites have shown exceptional print quality, resulting in cell performance similar to the commercial paste. Accelerated thermal cycling tests on mini-modules constructed from aluminum back surface field (Al-BSF) cells show a slower degradation rate for the cells integrated with the composite grid fingers and busbars for the front surface metallization compared to the cells with conventional metallization.
