A few people have asked recently what exactly is going on inside the PN junction. What concretely is happening? How can we leverage students’ previous knowledge about current and charge?

I made these videos because I wasn’t satisfied with the textbook or the available resources. No math; just a heuristic blow-by-blow focusing on electrons, physical force, and causality. The production value ranges from amateur to terrible. But the content is what underlies everything from transistors to solar panels to logic gates.

A series of 11 short videos uses this slide deck (also available in *.PDF).