Shining Light on Solar Cells - Chapter 9.0: Multi-junction (Tandem) Solar Cells

Multi-junction/tandem solar cells are created in an effort to surpass the Shockley Queisser Limit. You can learn more about this limit in Chapter 5.1. Instead of one layer of pn junction, multijunction solar cells employ two junctions. The top junction is a high bandgap solar cell to absorb high-energy photons, while the bottom junction is a low-bandgap solar cell to absorb low-energy photons. This way, we get more voltage from solar cells, eventually leading to possibilities of surpassing the Shockley Queisser Limit.

Image from PV Education

While the concept of multi-junction solar cells is easy to understand, the actual design is more complex than that. In this video, let us explore two design areas in multijunction solar cells: lattice-matching and current-matching. Enjoy the video!

Other parts in this series:

• Chapter 1.0: Introduction
• Chapter 2.0: Semiconductor Physics (Band Diagram, Free Carriers)
  • Chapter 2.1: Semiconductor Physics (Doping)
  • Chapter 2.2: Semiconductor Physics (Fermi-Energy Level)
• Chapter 3.0: PN Junction diode (Drift and Diffusion)
  • Chapter 3.1: PN Junction diode (Forward & Reverse Bias, IV Curve)
• Chapter 4.0: Photons
• Chapter 5.0: How do Solar Cells Work? (Working Principle, IV Curve, Photovoltaic Parameters, Solar Cell Datasheet)
  • Chapter 5.1: How do Solar Cells Work? (Typical Structure, Shockley-Queisser Limit)
• Chapter 6.0: How are solar panels made? (From quartz to silicon wafers)
  • Chapter 6.1: How are solar panels made? (From silicon wafers to solar panels)
• Chapter 7.0: PV Systems and Costing 101
• Chapter 8.0: Thin Film Solar Cells

Further reference materials that I highly recommend:

Luque, A. and Hegedus, S. (2003). Handbook of Photovoltaic Science and Engineering. John Wiley & Sons. ISBN: 978-0-471-49196-5.