Crystalline dioctyl‐3, 4, 9, 10‐perylenedicarboximide nanowires and 6, 13‐bis (triisopropylsilylethynyl) pentacene microplates are integrated into a vertical‐yet‐open asymmetrical heterojunction for the realization of a high‐performance organic photovoltaic detector, which shows fast photoresponse, ultrahigh signal‐to‐noise ratio, and high sensitivity to weak light.