It would be interesting to see follow-up video about comparing those old photocells to cutting edge technology, and to normal new calculators to see how much solar power technology have developed. I think that power consumption have gone down, and not the photocells, but we have also battery charger etc. using solar cells so I'm not 100% how they work, does they have higher cell voltage and efficient switch mode converter to produce higher charging current or what?
I had similar calculator as the last calc shown in video, brilliant device. I also took it apart when I got it, very interesting construction. It's photocell couldn't power it in classroom and without battery it were useless. Then I bought TI-92 which I'm using still at this moment, sucks battery 8mA when idling and 40mA doing some processor intensive calculation! Always crying backup batteries in my schoolbag