The Mystery Flaw of Solar Panels
Real Engineering・13 minutes read
The global capacity of solar cells has increased annually, reaching 630,000 megawatts by 2019, but light-induced degradation has been reducing efficiency, leading to a significant loss of potential electricity. Engineers have focused on optimizing silicon solar cells by minimizing light reflection, doping with boron and phosphorus, and addressing boron-oxygen defects to improve overall efficiency.
Insights
- Light-induced degradation, a long-standing issue in solar cell technology, has been a significant factor in reducing efficiency levels shortly after operation, prompting research into preventing boron-oxygen defects that hinder electron flow and developing effective prevention techniques.
- Silicon's role as a preferred material for solar cells stems from its semiconductor properties, with efforts concentrated on minimizing light reflection to enhance absorption and boost efficiency, showcasing the importance of material properties and design optimization in maximizing solar energy conversion.
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Summary
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Solar Cell Efficiency: Advances and Challenges
- Global capacity of solar cells has increased annually for the past decade due to falling prices and improved efficiency, surpassing 630,000 megawatts by the end of 2019.
- Despite advancements, a 40-year-old issue known as light-induced degradation has been reducing solar cell efficiency from 20% to 18% within hours of operation, resulting in a significant loss of potential electricity.
- Photovoltaic cells utilize the photovoltaic effect, where photons striking a material can free electrons to generate a current, with selenium being an early material used for solar cells but with low efficiency.
- Silicon, a semiconductor, became a preferred material for solar cells due to its properties, with efforts focused on minimizing light reflection to enhance absorption and increase efficiency.
- Silicon requires photons with 1.1 electron volts to produce the photovoltaic effect, limiting the usable solar energy spectrum and causing losses, with silicon balancing these factors effectively.
- To create an electrical current, silicon is doped with boron and phosphorus to form p-type and n-type materials, respectively, which when combined create a solar cell that generates electricity.
- Metal contacts on solar cells can block light, reducing efficiency, leading engineers to optimize the design to minimize coverage while maintaining low resistance for electron flow.
- Efficiency drop from 20% to 18% after operation was linked to boron-oxygen defects in silicon wafers, with research focusing on reducing oxygen impurities to prevent defects that hinder electron flow.
- A breakthrough in understanding the defect creation process revealed boron-oxygen molecules transforming into shallow acceptors under light exposure, acting as recombination sites, allowing engineers to develop better prevention techniques.
