What is a solar-powered watch/clock?

A solar-powered watch/clock is a watch/clock that is powered by a solar cell, which converts light from the sun, or fluorescent lights, etc., into electrical energy.
As shown in the figure below (wristwatch example), when the dial of the watch is exposed to light, the built-in solar cell generates electrical energy and stores it in the secondary cell (rechargeable battery) as a power source to run the watch. A solar-powered watch/clock is an ecological watch/clock that is friendly to people and the earth, harnessing non-polluting energy sources such as sunlight and using a rechargeable battery with the aim of reducing environmental burden.

* Unlike a disposable battery (primary cell) such as dry battery and button battery, a secondary cell (rechargeable battery) is an earth-conscious electric cell that can be used over and over for a long period of time by recharging.