We have investigated the visible/near-infrared photodetectors based on the nipip HIT structure. The responsivities of the nipip photodetectors were compared with the pinin photodetectors. The nipip structure has a better near-infrared response; meanwhile the pinin structure has a better blue response. At 1 V, the responsivities of the typical nipip HIT structure could achieve 0.478, 0.530, and 0.667 A/W at the wavelengths of 450, 650, and 850 nm, respectively. The thicker top a-Si:H(i) would not prevent the hole collection for the nipip structures. If the thickness of top a-Si:H(i) can be appropriately increased, the responsivities would be further enhanced. (C) 2012 Elsevier B.V. All rights reserved.