2D Materials‐Based Photodetectors with Bi‐Directional Responses in Enabling Intelligent Optical Sensing

With the rapid advancement of 2D material‐based optoelectronic devices, significant progress is made in the development of all‐optical logic devices, synaptic biomimetic devices, and multidimensional detection systems. As entering to the high‐speed information era, there is an urgent demand for complex, compact, multifunctional, low‐energy, and high‐speed intelligent sensing chips. Examining the evolution of current technologies reveals a parallel in the advancement of bipolar response mechanisms‐from simple positive and negative responses to more intricate inhibition‐promotion dynamics with persistent characteristics. This evolution significantly broadens their applications in biomimetic devices. Moreover, compared to unipolar responses, complex bipolar responses offer greater flexibility in adaptation and a unique one‐to‐one mapping with high‐dimensional information parameters such as polarization, phase, and spectrum, positioning them as promising candidates for breakthroughs in multidimensional detection and resolution. In this review, design strategies are comprehensively explored for various bipolar responses in 2D materials, highlighting their deep applications and progress in advanced fields. It is aimed for this review to provide a broad overview of bi‐directional response mechanisms, offering inspiration for designing the next generation of intelligent sensing chips.