Root-cause analysis and characterization of oxygen-related defects in silicon PV material : an approach from macro to nanoscale

Abstract

With energy demand forecasted to grow significantly, efforts towards mitigating global warming effects by reducing greenhouse gas emissions are becoming stricter as more power generation plants are deployed to meet the global demand. Deployment of renewable energy technologies as a low-carbon alternative to fossil fuel is an attractive solution. Photovoltaics (PV) present several advantages over other energy sources because PV is modular, and has proven to be a scalable and reliable technology. A capital expenditure reduction of 70% has been found to be necessary to meet the climate targets of 7-10 TW of PV by 2030. This can be achieved through different channels: improving conversion efficiency and device performance of silicon modules, increasing solar cell manufacturing yield, reducing silicon feedstock material use, etc. This research focuses on n-type monocrystalline silicon and aims to increase conversion efficiency up to 20% relative and increase manufacturing yield up to 50%, as levers to reduce the capital expenditure. The increase in conversion efficiency and manufacturing yield is achieved by defect engineering and mitigation of a lifetime-limiting bulk defect in n-type monocrystalline silicon, characterized by low-lifetime concentric rings. Temperature- and injection-dependent photoluminescence imaging is applied to investigate the defect's root-cause by studying its evolution under several high temperature process conditions and is found to be caused by oxide-related precipitates. Synchrotron-based mic ...