Lighten up and feel the force

The idea that we might use sunlight to make a significant fraction of our electricity has enjoyed sustained popularity in the three decades since the October 1973 Yom Kippur war and the ensuing "oil shock". Remarkably, this dream may be achieved in the next decade or two. Worldwide, commercial production of solar cells is growing at a rate of about 25 per cent a year, and the cost of generating solar electricity has fallen nearly 30-fold since 1973.

While quite a few books have been written about solar electricity for a popular readership, and even more monographs and handbooks have been issued for a technical readership, Jenny Nelson's The Physics of Solar Cells is apparently the first to become widely available for undergraduate students studying physics and engineering.

Universities around the world now offer specialised classes on this topic, attracting many students interested in solar energy. Courses cover an intriguing range of topics, including semiconductor and transport physics, thermodynamics and optics.

Nelson's book should be a good text for such classes. Her writing is lucid and lively, and she sustains a consistent level of sophistication throughout. The text is generously illustrated with figures.

One aspect of the book that I particularly valued is its accessible treatment of "solar cell thermodynamics". The introductory chapters treat solar energy conversion from a very fundamental, energy-conversion perspective, and Nelson returns to this area for her final chapter on "over-the-limit" strategies for solar electricity generation. She also includes a chapter on "photon management", which is the crucial art of optimising the absorption of incident sunlight in the thinnest possible slice of semiconductor material.

The middle section contains a reasonably self-contained introduction to conventional semiconductor physics and semiconductor device physics. Both material and level are comparable to other textbooks on the subject, but Nelson puts greater emphasis on topics that are important in solar cells.

The section focuses on the opto-electronic properties of crystals; non-crystalline materials receive less attention.

Two topical chapters introduce specific materials employed in present solar-cell technologies. These range from single crystals of silicon and gallium arsenide, through polycrystalline alloys, to non-crystalline materials such as amorphous silicon.

Undergraduates with little background knowledge of quantum mechanics, statistical mechanics, and solid-state physics are likely to find the book somewhat indigestible; instructors using the book as a text with such students should be prepared to expand on its treatment of some subjects.

Nelson provides 13 exercises (with solutions) within the text, which should provide instructors with a good basis for developing weekly homework assignments.

Eric A. Schiff is professor of physics, Syracuse University, New York, US.