The AlGaN-based deep ultraviolet (DUV) light-emitting diode (LED) is an alternative DUV light source to replace traditional mercury-based lamps. However, the state-of-the-art DUV LEDs currently exhibit poor wall-plug efficiency and low light output power, which seriously hinder their commercialization. In this work, we design and report a tunnel-junction-cascaded (TJC) DUV LED, which enables multiple radiative recombinations within the active regions. Therefore, the light output power of the TJC-DUV LEDs is more than doubled compared to the conventional DUV LED. Correspondingly, the wall-plug efficiency of the TJC-DUV LED is also significantly boosted by 25% at 60 mA.