Diodes have been widely studied as one of the most commonly used electronic components in circuits, and it is important to find diodes with an excellent rectification performance. Herein, we investigate the electronic and transport properties of Schottky contact diodes based on zigzag hydrogenated blue phosphorene nanoribbons, by employing density functional theory combined with the non-equilibrium Green's function. It is found that the adsorption of transition metal atoms Sc/Cr/Ti and Ni on the top site of blue phosphorene nanoribbons leads to metallic and semiconducting properties, respectively. Devices consisting of the planar contact of the metallic and semiconducting nanoribbons show rectifying behavior due to the Schottky barriers of the homojunctions. The current is preferential to flow from the semiconducting side to the metallic side. The rectification ratio of the Sc–Ni device and the Cr–Ni device can reach up to 10⁸, which is much higher than that of traditional p–n junctions of about 10⁵–10⁷. The high rectification ratio at low bias regions, together with the low threshold voltages and negligible reverse currents, make blue phosphorene nanoribbon homojunctions ideal rectifier diodes.