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Abstract We study a generic model in which the dark sector is composed of a Majorana dark matter χ 1, its excited state χ 2, both at the electroweak scale, and a light dark photon Z′ with m z′ ∼ 10 −4 eV. The light Z′ enhances the self-scattering elastic cross section χ 1 χ 1 → χ 1 χ 1 enough to solve the small scale problems in the N-body simulations with the cold dark matter. The dark matter communicates with the SM via kinetic mixing parameterized by ϵ. The inelastic scattering process χ 1 χ 1 → χ 2 χ 2 followed by the prompt decay χ 2 → χ 1 Z′ generates energetic Z′. By setting δ ≡ m χ2 − m χ1 ≃ 2.8 keV and ϵ ∼ 10 −10 the excess in the electron-recoil data at the XENON1T experiment can be explained by the dark-photoelectric effect. The relic abundance of the dark matter can also be accommodated by the thermal freeze-out mechanism via the annihilation χ 1 χ 1(χ 2 χ 2) → Z′Z′ with the dark gauge coupling constant α X ∼ 10 −3.