Figure 5.

Electroluminescence (EL) from the WSe₂/MoS₂ heterojunction p–n diode. (a) The false color EL image of the heterojunction device under an injection current of 100 μA. The purple dashed line outlines the ML-WSe₂, the blue dotted line outlines the MoS₂ and the golden solid line outlines the gold electrodes. (b) The EL spectra of a ML-WSe₂/MoS₂ heterojunction at different injection current. (c) The EL spectra of a BL-WSe₂/MoS₂ heterojunction at different injection current. (d) The EL intensity as a function of injection current for both ML- and BL-WSe₂/MoS₂ heterojunction. (e) The ideal band diagram of the WSe₂/MoS₂ heterojunction under small forward bias. The conduction band in MoS₂ is below that in WSe₂, the valence band in WSe₂ is below that in MoS₂. At small bias, holes can go cross the junction and inject into n-type region, while the electrons cannot go cross the junction. (f) The ideal band diagram of the WSe₂/MoS₂ heterojunction under large forward bias. The conduction band in MoS₂ shifts upward and is higher than that in WSe₂, and the valence band in WSe₂ is below it in MoS₂. At large bias, both electrons and holes can go cross the junction and inject into the other side of the heterojunction. (g) The EL spectra of a ML-WSe₂/MoS₂ heterojunction at different temperature ranging from 25 to 75 °C. (h) The EL spectra of a BL-WSe₂/MoS₂ heterojunction at different temperature ranging from 25 to 75 °C. The injection current is fixed at 250 μA. (i) The normalized intensities of A and B′ peaks in the EL spectra of both ML- and BL-WSe₂ as a function of temperature.