Luminous paint
A  radioactive substance can be used; the energy of this radioactive decay can be converted into visible light. Today, the radiation of these substances is shielded easily, since the substances used only emit alpha radiation, or low-energy beta radiation. At the beginning of the 20th century, radium isotopes were used, which led to a number of cases of radiation poisoning; one of the most prominent cases is that of the Radium girls.