ZnO-based photodetectors (PDs) have long response times at magnitude of tens to hundreds of seconds, hampering their practical UV detection. The slow oxygen chemisorption/desorption process is the main cause of the slow response of UV PDs based on single ZnO nanowires (NWs). Here, the authors find the response speed of ZnO NW-based UV PDs could be improved by directly fabricating UV PDs on entangled ZnO NW array grown on SiO2 through a catalyst-free chemical vapor deposition (CVD) process. Specifically, the interconnections in ZnO NW array creates NW-NW junction barriers, which dominate the inter-wire charge transport. The switching of UV illumination induces fast tuning of NW-NW junction barrier height, which contributes to the enhanced response speed of the ZnO NW array UV PDs.