Abstract: Intrinsically anisotropic photoelectric materials have the capability to combine light detection with polarization sensing, which is essential for advancing next-generation polarization-dependent optoelectronic devices. However, achieving both a high anisotropy ratio and superior photoresponse in current materials remains challenging, creating a need for effective regulation techniques. Here, a novel paradigm is presented for applying pressure as a regulating knob to enhance both photoresponse and its anisotropy by overcoming the limitation imposed by the inherent in-plane bonding anisotropy of ZrSe₃. In situ high-pressure experiments show that the photoresponsivity along the a/b-axis increases by three orders of magnitude within 0.1-16.0 GPa, while its anisotropy ratio improves from 0.9 to 1.7. First-principles calculations confirm that the enhanced electronic coupling between Se-Se dimers along the a-axis under pressure promotes photo-generated carriers' transport and separation, leading to higher photoresponse than along the b-axis. In addition, ZrSe₃ exhibits a rare self-driven positive-negative photocurrent transition at approximately 7.4 GPa, which can well detect the pressure-induced n-p conduction switch in photoelectric materials. This study employs ZrSe₃ as a model material and opens up a new approach for pressure to regulate photoresponse anisotropy and, more broadly, provides valuable insights into materials design toward extraordinary properties.

Key words: Pressure regulation, In-plane anisotropy, Photoresponse enhancement, Se-Se dimer, Electronic coupling