Here's a popular educational solar robot kit recommended to everyone!

DIY Kit: With box package, powered by the sun, no battery required

This is a solar energy toy harboring the environmentally-friendly conception which can be assembled into 7 different robot modes.
Axel: The big-wheel solar robot, rolls along on two giant wheels.
Major: The drumming solar robot, marches to the beat of its own drum.
Tank: The tank solar robot, excels at roving over rough terrain with its tread-like feet.
Armie: The armadillo solar robot,is a master of somersaults and tumbling.
Dizzy: The spinning solar robot, manages to twirl endlessly in circles without getting dizzy.
Zoomer: The race-car solar robot, races along long, flat straightaways.
Cricker: The bug solar robot, crawls along on six legs.

Children can assemble these modes by themselves,to understand the theory of mechanical tramsmission and explore the secret of clean energy.
They can also gain understanding of the whole process of converting light energy into electrical energy
It will foster their interest in science and improve their environmental awareness.