This Letter presents a novel low-cost light detector based on radial silicon nanowire heterostructures. Photoelectrochemical responses of silicon nanowire arrays with different morphologies, prepared by a metal assisted chemical etching method, have been systematically investigated. The photoresponsivity of the black silicon nanowire arrays is 73 times larger than that of the planar silicon at 0.2 V bias under white light illumination. The relationship between the photoresponsivity and nanowire morphology and doping level is discussed. Our results demonstrate that the heterostructures of the nanowire arrays with an optimized morphology are promising for light detection and other optoelectronic devices. (C) 2012 Elsevier B.V. All rights reserved.