(A) Photoluminescence and (B) electroluminsecence in low-dimensional and 3D perovskite-based devices. Photoluminescence (PL) refers to the emission of light caused by the absorption of incident photons, whereas electroluminescence (EL) is the emission of light owing to the energy supplied by an electric current. Although low-dimensional perovskite exhibits better PL properties than 3D perovskite, the latter has better EL properties, which can be exploited to design very bright and efficient PeLEDs.