Solar panels on calculators, as well as on many small electronic devices, typically use amorphous silicon (a-Si) solar cells. These solar cells are made of thin layers of amorphous silicon deposited on a substrate, such as glass or a flexible material. The amorphous silicon solar cells are known for their lightweight and low-cost manufacturing, which makes them suitable for powering small electronic devices like calculators.

Amorphous silicon solar cells are less efficient compared to other types of solar cells like monocrystalline or polycrystalline cells, but they are well-suited for low-power applications where space and weight constraints are important. They can generate electricity even in low-light conditions, making them suitable for indoor use as well.

The thin, flexible nature of amorphous silicon solar cells allows them to be integrated into the design of calculators and other devices without adding significant bulk or weight. This makes them a practical choice for powering these types of portable, low-power electronics.