Common crystals that generate electric currents when exposed to light

 Yesterday, I came across an interesting word in the dictionary: actinoelectric. It is an older word defined in the dictionary as "exhibiting photoconductivity." It was used in the 1920s and 1930s and then apparently fell out of use (see https://books.google.com/ngrams/graph?content=actinoelectric&year_start=1800&year_end=2022&corpus=en&smoothing=3). 

Photoconductivity is "an optical and electrical phenomenon in which a material becomes more electrically conductive due to the absorption of electromagnetic radiation such as visible light, ultraviolet light, infrared light, or gamma radiation" (https://en.wikipedia.org/wiki/Photoconductivity).

However, when I looked up more information on "actinoelectric," I found out that actinoelectric materials don't just exhibit photoconductivity. They actually generate electric current when exposed to light. They are photovoltaic, too. 

And this was known as early as 1929, based on the existence of a journal article reporting light being used to generate an electromagnetic force in selenium. See Robert L. Hanson, "The Photo-emf in Selenium*," J. Opt. Soc. Am. 18, 370-382 (1929). https://opg.optica.org/viewmedia.cfm?r=1&rwjcode=josa&uri=josa-18-5-370 (no abstract available online).

Here is a 1939 study reporting generation of an electrical current in tartaric acid crystals. Grapes are high in tartaric acid, and tartaric acid crystals are contained in grape products, including wine and raisins. Tartaric acid is also high in tamarind.

Abstract: Tartaric acid crystals illuminated with light from a carbon arc exhibit a flow of current when connected to a galvanometer without the aid of an impressed battery. This actinoelectric effect is greatly dependent upon the orientation of the crystal with respect to the illuminating beam of light. It is shown that a section of the crystal can be chosen which shows a series of equi-potential lines when its surface is examined with two probes while the crystal is illuminated. The measured currents are about 10−12 ampere, when the crystal is illuminated with the light from a carbon arc. The effect is a linear function of light intensity for the lower light intensities, but increases more rapidly for higher intensities. The effect is practically independent of temperature in the range from 20°C to -40°C. The maximum spectral response is at approximately 10,500A

Brady, J.J. and Moore, W.H. Actinoelectric Effects in Tartaric Acid Crystals. Phys. Rev. 55, 308. Published 1 February, 1939. DOI: https://doi.org/10.1103/PhysRev.55.308

We have this idea that photovoltaic materials have to be expensive components in solar panels and the like. But if everyday items like crystals in raisins and tamarind, when exposed to the right kind of light at the needed angles, can generate electromagnetic fields in the human body, that is something we should know and use, given how many functions of our bodies are connected to electromagnetism.

Perhaps one of the reasons we enjoy certain kinds of chandeliers and light fixtures more than other kinds is connected to whether they produce light in desirable wavelengths for crystals in our eyes and skin. A lot of women tan (i.e., lay in the sun or a tanning bed) because it makes them feel good.