We report the development of efficient small molecular organic photovoltaic devices incorporating tetracene anode interfacial layers. Planar heterojunction devices employing the tetracene anode interfacial layer achieved an EQE enhancement of 150% in the spectral region corresponding to ZnPc absorption. We demonstrate that this enhancement is due to the combined effect of the tetracene layer providing exciton-blocking at the anode/donor interface and potentially an increase in the exciton diffusion length in the ZnPc layer due to increased crystallinity and more preferred molecular stacking orientation. A power conversion efficiency of 4.7% was achieved for a planar heterojunction of a modified zinc phthalocyanine based material and C60 when employing the tetracene anode interfacial layer. By utilizing a planar-mixed heterojunction structure a peak EQE of nearly 70% and a power conversion efficiency of 5.8% was achieved.