The efficiency of any electronic device is highly reliant on the charge-injection efficiency at the electrical contact and semiconductor interface. Black phosphorus (BP), a layered and highly anisotropic material is attractive for a variety of electronic and optoelectronic applications including vertically stacked devices with distinct top and bottom electrodes. This makes it imperative to ascertain the influence of contact materials on the charge injection in the out-of-plane configuration. Here, we explore four different contact materials (aluminium, ITO, gold and platinum) chosen based on their work functions relative to the chemical potential of BP. By monitoring the current-voltage characteristics in the out-of-plane direction, conclusions are drawn regarding the charge injection capabilities of these contact materials providing the base knowledge to design efficient BP based stacked devices