Photodetectors come in a wide variety of constructions and materials, with the Cu2O-based photodetector that [Mad Scientist Creations] demonstrates in a recent video being a good example of a photodetector that can be created at home using nothing but some copper and a heat source.
Of the two copper elements in a salt water cell, one element is heated to the point where a copper oxide layer forms, specifically Cu2O, which acts as a semiconductor and provides the photosensitive layer. Even a fairly crude sensor created with a regular gas stove produces enough of a current that it can be used in a simple light detection circuit.
Although copper-oxide photodetectors may seem quaint, they are getting a lot of interest as they feature a very narrow bandgap at 1.2 eV. In a 2019 study by [Hyeon-Joo Song] et al. as published in Scientific Reports such a sensor is enhanced with an optimized grain structure that improves its performance, with much higher sensitivity and faster response times.
As demonstrated by [Andrzej Kwiatkowski] et al. in a 2024 paper in Solar Energy Materials and Solar Cells these copper-oxide sensors can also be used for gas detectors, though they used advanced gas deposition to produce the thin films instead of sticking a bit of copper tape into a natural gas flame.
Even if DIY copper-oxide sensors aren’t quite as exciting as what one can do with access to a well-equipped (semiconductor) lab, it’s still a pretty accessible material that lends itself for easy experimentation.
