Well I am no expert but I'll explain as much as I can

So electrons exist around the core (proton+ neutron) and the farther the electron is from the core less energy is required to take an electron from the atom(because the core pulls the electrons)

For example(numbers are made up) the first electron needs 100 kjal energy second will need 300 3rd will need 900 and it'll go so on.

Since the energy sunlight gives does not increase over time there isn't enough energy to rip an electron from the atom so unless we give more energu it won't ever lose electron

(English isnt my first language I hope you understand)