Bench Degree·SOLAR POWERchapter

On the Cover

How the cover of every Bench Degree volume is chosen. One question, and it is not who got there first or who is famous. If we could bring anyone back to teach you this subject, who would you actually want at the bench? That is the whole test. It picks people who did the work with their hands, who checked things themselves, and who would be worth standing next to. Every one of them actually lived, which is why a cover portrait in this series is either a real document or openly a drawing, and never a photograph of something that did not happen.

Edmond Becquerel, engraved from a portrait held by the Bibliothèque nationale de France.

In 1839 he put two coated metal plates into an acid solution, shaded one, let sunlight fall on the other, and watched a current appear between them. That is the photovoltaic effect, and it is the whole of this book. He was nineteen years old, he was working in his father’s laboratory, and the apparatus was a jar of liquid.

He is not here for the priority. He is here because of what the apparatus was. The subject did not begin in a clean room. It began in a wet cell with an asymmetry in it, one side treated differently from the other, and every panel on every roof is still that asymmetry moved into solid silicon. Chapter 3 has you build a cell in a jar of salt water for about $10, which is as close to his laboratory as this series can put you.

And he is here because he was nineteen. Not a professor, not a laureate, not a man with a budget. A teenager in his father’s laboratory, working with jars and plates and acid, who noticed that light falling on one electrode and not the other made a current flow, and who then did the part that separates a discovery from an accident: he wrote it down carefully enough that other people could repeat it. He measured how the current changed with the colour of the light. He noticed it depended on which coating he used. That is not luck. That is method, at an age when most people are still being told what to think.

The effect he found stayed unexplained until Einstein in 1905 and unusable until Bell Labs in 1954, and plenty of better-equipped people spent the intervening century making it work. Daryl Chapin, who built the first practical silicon cell, gets Chapter 3 for exactly that reason. But the thing itself was found by a nineteen-year-old in a wet cell, and if you could have one person at your bench while you built your first working cell, you would want the one who found it with almost nothing and still described it properly.

About the portrait. The source is a nineteenth-century portrait of Becquerel in the collection of the Bibliothèque nationale de France, in the public domain by age. A program converts it to line work, setting each line thickness from the local tone of the original, which is arithmetic on a real document. No generative model touched it, and no part of his face has been altered or completed.

The rule for this series is that a cover portrait is a document or it is openly a drawing, and it is never a photograph of something that did not happen.

The full account of how this book was made, including which parts were written with the help of a language model, is on the copyright page and on the back cover, itemised using the five credits published at bookcredits.org.

Bench Degree

Get the degree without the diploma.

Learn the material, not how to pass the exam.