From the Photovoltaic Effect to Photoelectric Solar Cells

The Industrial Revolution changed the world—not only the economy but also our daily lives. The growing use of alternative energy sources is changing the world in the same way. Whether we call it the green revolution, the ecological transition, the shift to alternative energy sources, or the course of history, it does not change the fact that we have entered a new era.

Energy consumption has grown faster than the population over the past forty years, and this trend is expected to accelerate during the first half of the 21st century, largely due to growth in China and India. There are two solutions: reducing consumption and utilizing new energy sources.

However, these alternative energy sources must meet a new requirement: they must not contribute to global warming. Among these energy sources, nuclear power is generally distinguished from the others: wind, biomass, hydroelectric, solar (thermal and photovoltaic), and geothermal.

Solar energy is one of these alternative energy sources. It is poised to become one of the major energy sources of the future due to the world’s shift toward electrification. Photovoltaic energy already has a track record of major achievements. In fact, it provided the energy needed for space exploration; without photovoltaic energy, there would be no International Space Station, and no Spirit or Opportunity rovers on Mars.

But the photovoltaic energy sector is also a high-tech field that is rapidly evolving in a fast-growing market and requires not only strong scientific and technical skills but also an understanding of legislative, political, and societal issues. It therefore represents a fantastic field of opportunity for engineers of the 21st century.

In order to make a meaningful contribution to its development, it is necessary to start with the source of this energy—the Sun—and consider the factors that determine the corresponding ground-level potential. The first part of this article will focus on this topic. This energy must then be converted into electricity using a photovoltaic cell.

The second part will therefore be devoted to the study of the photovoltaic cell, the heart of the conversion system. To understand how it works and the parameters that govern the performance of this conversion, we will begin with a review of semiconductor physics. We will then discuss light absorption by a semiconductor and the photovoltaic conversion carried out by a p-n junction. Information regarding the materials that make up these pn junctions in photovoltaic devices will then be provided; on silicon, of course, but also on less commonly used materials, both in bulk form and as thin films. This second part will conclude with a discussion of the technologies...