(color online) (a) Schematic of the MoS₂/silicon heterojunction electroluminescence device (top). Electroluminescence spectra of a MoS₂ diode at room temperature (bottom left) and low temperature (bottom right), respectively.^[95] (b) Schematic of the p+-Si/i-WS₂/n-ITO heterojunction LED device (top). Electroluminescence spectra of the LED device recorded at 77 K under different injection current (bottom).^[96] (c) Schematic illustration (top left) and electroluminescence image (top right) of the WSe₂/MoS₂ heterojunction p–n diode. The electroluminescence spectra of a bilayer WSe₂/MoS₂ heterojunction at different injection current (bottom).^[97] (d) Schematic of the single-quantum-well (SQW) heterostructure (top left). Schematic of the heterostructure consisting of Si/SiO₂/hBN/GrB/3hBN/MoS₂/3hBN/GrT/hBN (top right). Temperature dependence of EQE for a device with two quantum wells (QWs) made from MoS₂ and WSe₂ (bottom left). Band diagrams for the case of zero applied bias for the heterostructure are shown in the top right panel (bottom right).^[98]