Tandem solar cells, particularly those combining perovskite with silicon, enhance the efficiency of solar panels by utilizing two or more types of solar cells stacked together. Each layer is optimized to capture a specific part of the solar spectrum, allowing them to convert more sunlight into electricity than traditional single-layer solar cells. Here’s how they improve efficiency:
Key Mechanisms of Improvement
- Spectrum Utilization: Tandem cells split the solar spectrum into parts that are matched to the energy gap (bandgap) of each sub-cell. This allows each sub-cell to convert the portion of the spectrum it is optimized for most efficiently.
- Increased Efficiency Potential: By stacking multiple layers, tandem cells can achieve higher power conversion efficiencies than single-junction cells. Theoretical efficiencies for tandem cells can reach up to 44%, significantly higher than the efficiencies of most single-junction solar cells.
- Reducing Energy Loss: In single-junction cells, photons with energy higher than the bandgap are lost as heat. Tandem cells capture more of this energy by having layers with different bandgaps, reducing thermal losses.
Types of Tandem Configurations
- Two-Terminal Tandems: These require both optical and electrical matching between the sub-cells, limiting the range of bandgap combinations but simplifying the fabrication process.
- Four-Terminal Tandems: These require only optical matching, allowing greater flexibility in bandgap selection but are more complex to connect and use.
Challenges and Advances
- Reliability and Scalability: Current challenges for perovskite/silicon tandem cells include improving their reliability in the field and scaling up production while maintaining high efficiency levels.
- Recent Breakthroughs: Recent advancements have pushed the efficiency of perovskite-silicon tandem cells to over 32.5%, making them closer to commercial viability.
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