Electricity from Sunlight, 2nd Edition

2Solar Cells

2.1 Setting the Scene

We are now ready to discuss the underlying principles and operation of the invention central to our story—the modern solar cell. To help set the scene, we shall also say a few words about photovoltaic (PV) modules, reserving a detailed discussion for the next chapter. It will be helpful to start this chapter with a brief account of the main types of solar cell and module in widespread use today.

Silicon solar cells have been the workhorse of the PV industry for many years and currently account for well over 80% of world production. Modules based on these cells have a long history of rugged reliability, with guarantees lasting 20 or 25 years that are exceptional among manufactured products. Although cells made from other materials are constantly being developed and some are in commercial production, it will be hard to dislodge silicon from its pedestal. The underlying technology is that of semiconductor electronics: a silicon solar cell is a special form of semiconductor diode. Fortunately, silicon in the form of silicon dioxide (quartz sand) is an extremely common component of the Earth’s crust and is essentially nontoxic. There is a further good reason for focusing strongly on silicon cells in this chapter: in its crystalline form silicon has a simple lattice structure, making it comparatively easy to describe and appreciate the underlying science.

There are two major types of crystalline silicon solar cell in current high‐volume production: ...