Broadband photodetector has wide applications in the field of remote sensing,health monitoring and medical imaging.Two-dimensional (2D) materials with narrow bandgaps have shown enormous potential in broadband photodetection.However,the device performance is often restricted by the high dark currents.Herein,we demonstrate a high performance broadband photodetector by constructing Bi2O2Se/BP van der Waals heterojunction.The device exhibits a p-n diode behavior with a current rectification ratio of ～20.Benifited from the low dark current of the heterojunction and the effective carrier separation,the device achieves the responsivity (R) of ～ 500 A/W,～ 4.3 A/W and ～ 2.3 A/W at 700 nm,1310 nm and 1550 nm,respectively.The specific detectivity (D*) is up to ～ 2.8 × 1011 Jones (700 nm),～ 2.4 × 109 Jones (1310 nm) and ～ 1.3 × 109 Jones (1550 nm).Moreover,the response time is ～ 9 ms,which is more than 20 times faster than that of individual BP (～ 190 ms) and Bi2O2Se (～ 180 ms) devices.