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2D anisotropic materials, such as black phosphorus, ReS₂, and GaTe, have been shown to exhibit exciting direction‐ and polarization‐sensitive material properties. Highly crystalline chemical‐vapor‐transport‐grown ZrS₃crystals exhibit large optical‐absorption‐coefficient anisotropy, which doubles under resonance conditions. The observed optical anisotropy manifests itself in angle‐resolved photocurrent density polar plots with dichroic ratio (I_pb/I_pa) of 1.73 excited by a laser source of λ = 450 nm and 1.14 by λ = 532 nm. The optical absorption and electronic dichroic response are fully explained through detailed band structure and polarization‐sensitive optical‐absorption‐spectrum calculations. Not only is the family of 2D anisotropic semiconductors expanded into Zr‐based trichalcogenides but fundamental insights on how crystalline anisotropy, optical absorption dichroism, and generated photocurrents are interrelated in van der Waals Zr‐based trichalcogenides materials are also provided.

2D layered materials have emerged in recent years as a new platform to host novel electronic, optical, or excitonic physics and develop unprecedented nanoelectronic and energy applications. By definition, these materials are strongly anisotropic between the basal plane and cross the plane. The structural and property anisotropies inside their basal plane, however, are much less investigated. Black phosphorus, for example, is a 2D material that has such in‐plane anisotropy. Here, a rare chemical form of arsenic, called black‐arsenic (b‐As), is reported as a cousin of black phosphorus, as an extremely anisotropic layered semiconductor. Systematic characterization of the structural, electronic, thermal, and electrical properties of b‐As single crystals is performed, with particular focus on its anisotropies along two in‐plane principle axes, armchair (AC) and zigzag (ZZ). The analysis shows that b‐As exhibits higher or comparable electronic, thermal, and electric transport anisotropies between the AC and ZZ directions than any other known 2D crystals. Such extreme in‐plane anisotropies can potentially implement novel ideas for scientific research and device applications.