The first 200 people to sign up at https://brilliant.org/stevemould/ will get 20% off an annual subscription that gives you access to the full archive of Daily Problems and every single course. It looks like I may have been a little off on the explanation. Specifically attributing the movement of charge carriers exclusively to the electric field that build up. Read more about that here: https://www.quora.com/How-do-solar-cells-work/answer/Sjoerd-Smit-3 Animations by Dom Burgess. His brilliant channel, Every Think, is here: https://www.youtube.com/channel/UCGI000V6ZIAQf97MNybAaLQ Part 1 demonstration video is here: https://www.youtube.com/watch?v=6WGKz2sUa0w Photovoltaic cells and LEDs are both made of diodes. Diodes are designed to allow electricity to flow in one direction only but the way we make them (out of semiconductors) means that can absorb and emit light. Thanks to these amazing patrons on Patreon for supporting my channel: Glenn Watson Joël van der Loo Patreon: https://www.patreon.com/stevemould Twitter: http://twitter.com/moulds Instagram: https://www.instagram.com/stevemouldscience/ Facebook: https://www.facebook.com/stevemouldscience/ Buy nerdy maths things: http://mathsgear.co.uk/