Sure, it’s easier (and more practical) to buy a solar cell ready-made but this is much more fun.
It’s easy to cut open a power transistor like the 2N3055 to expose the NPN silicon material inside to make a solar cell. When exposed to sunlight, or household lights, it conducts electricity. The N-type and P-type materials work like a solar cell. The best way is from the Base to the Collector though from both the Base and Emitter combined and then to the Collector also works well. The voltage and current aren’t much but with just a few of them in series you can power a small 1.5 volt calculator.
Make a robot friend with Adafruit’s CRICKIT – A Creative Robotics & Interactive Construction Kit. It’s an add-on to our popular Circuit Playground Express, FEATHER and other platforms to make and program robots with CircuitPython, MakeCode, and Arduino. Start controlling motors, servos, solenoids. You also get signal pins, capacitive touch sensors, a NeoPixel driver and amplified speaker output. It complements & extends your boards so you can still use all the goodies on the microcontroller, now you have a robotics playground as well.