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In this letter, the ultraviolet light emitting diode (UV-LED) with an undoped Al0.23Ga0.77N electron-blocking layer (EBL) between the p-type doped Al0.23Ga0.77N EBL and last barrier was proposed. After inserting the undoped EBL, both the photoluminescence and electroluminescence (EL) characteristics of UV-LED were significantly improved. As the undoped EBL was inserted, the 365-nm UV-LED possessed 400% improvement in output power (at 19 A/cm2). However, the enhancement in output power was significantly reduced to 20% when the insertion of undoped EBL was applied for 375-nm UV-LED. In addition, the long-term reliability was enhanced efficiently with the addition of undoped EBL. After the aging test for 1032 h, it presented the 365-nm UV-LED inserted with an undoped EBL had the obvious improvements both in the characteristics of EL intensity and leakage current density.