In this work, n-GZO/a:amorphous-Si(i:intrinsic)/p+-Si photodiodes are fabricated. We employed a nanosphere lithographic technique to obtain nanoscale patterns on either the a-Si(i) or p+-Si surface. As compared with the planar n-GZO/p+-Si diode, the devices with nanopatterned a-Si(i) and nanopatterned p+-Si substrates show a 32% and 36.2% enhancement of photoresponsivity. Furthermore, the acceptance angle measurement reveals that the nanostructured photodiodes have larger acceptance angles than the planar structure. It also shows that the device with the nanocone structure has a higher acceptance angle than that with the nanorod structure.