Transition metal dichalcogenides (TMDCs) have shown tremendous potential for application in the field of optoelectronics owing to their extraordinary characteristics. The $\rm{WS_{2}/V_{0.25}W_{0.75}Se_{2}}$ van der Waals heterostructure was fabricated by layer transfer technique and its $I – V$ characteristic was measured at room temperature. The fabricated pn-junction heterostructure shows obvious current rectification with a rectification ratio of $\thicksim{39}$ at $\pm{1}$ V. The heterostructure was analysed in the dark and under polychromatic illumination. The noticeable rise in reverse current is observed at higher intensity of illumination. The photocurrent and photoresponsivity are found to be enhanced as intensity and bias voltage are increased. The higher value of the ideality factor of $\thicksim{2}$ is attributed to the inhomogeneity of the heterojunction.