Ultraviolet (UV) photodetectors have recently captured great attention due to their applications in various engineering fields such as pollution monitoring, secure space-to-space communication, and solar UV monitoring. In all of these practical applications, UV detectors need to possess a high signal-to-noise ratio, fast response and recovery time, high selectivity and stability, and acceptable responsivity (gain of a detector). As a direct wide-bandgap semiconductor, ZnO (Eg = 3.3 eV) has demonstrated promising properties for UV detection with a relatively high UV-to-visible rejection ratio (selectivity). Nevertheless, a major challenge that prevents designing high-quality ZnO-based photodetectors is their high dark current under externally applied bias. It was more recently demonstrated that the leakage current (dark current) across a Schottky barrier-based metal–ZnO detector can be effectively modified using external mechanical stresses, i.e. piezotronic and piezo-phototronic effects. In the present work, we consider the influence of externally applied loads on the photodetection properties of ZnO bicrystal as a modeled system. It is demonstrated that Double Schottky barrier (DSB) formed at the interface of ZnO bicrystals plays a key role in the induced photocurrent and can be noticeably modulated so as to improve the signal-to-noise character of the UV detector. Zinc oxide bicrystals, including various crystallographic configurations i.e. OIO, OIZn, and ZnIZn, were prepared using a diffusion bonding technique followed by a high-temperature epitaxial solid-state transformation step, resulting in a single boundary between two crystals. Electrical conductivity evaluations illustrated all the prepared bicrystal systems featured varistor-like behavior, proving the formation of a double Schottky barrier at the grain boundary with a height of 0.9 eV and approximate breakdown voltage of 3.7 V. Moreover, it was shown that the I-V characteristics of the samples are highly stress-dependent, which greatly influenced the dark current amplitude and subsequently the UV photodetection performance of the systems. The origin of the photoresponsivity change with mechanical load and crystal orientation is explained according to the modification of the formed double Schottky barrier.