Low‐Symmetry 2D Ta₂PtSe₇ Induced by Ultralong Structural Motifs for Flexible Long‐Wave Infrared Photodetection up to 10.6 µm

Abstract

AbstractThe limited ability of traditional 2D anisotropic materials to meet next‐generation anisotropic device demands necessitates innovative design strategies. To address this challenge, a symmetry‐reduction approach is proposed that enhances in‐plane anisotropy by extending structural motifs to lower crystal symmetry. Implementing this design principle, a novel van der Waals material, Ta2PtSe7 atomic layers is successfully developed, featuring record‐breaking [Ta4Pt2Se14] structural motifs with an unprecedented length of 20.1 Å. This unique architecture endows Ta2PtSe7 with remarkable intrinsic in‐plane anisotropy, manifesting in strongly direction‐dependent optical and electrical characteristics. The developed Ta2PtSe7‐based photodetector demonstrates exceptional broadband responsiveness across an expansive spectral range from visible to long‐wavelength infrared (LWIR; 671 nm–10.6 µm). Particularly noteworthy is its outstanding performance under low operating voltage (0.1 V), achieving a high responsivity of 27 V W−1 at 10.6 µm illumination – a significant advancement in LWIR detection capabilities. Furthermore, flexible device configurations exhibit excellent mechanical robustness, maintaining over 70% of initial photocurrent after 50 bending cycles, demonstrating promising potential for flexible optoelectronics. This study proposes a novel structural motif engineering strategy to design anisotropic materials, exemplified by Ta2PtSe7’s exceptional in‐plane anisotropy, broadband photoresponse, and mechanical robustness, enabling high‐performance anisotropic optoelectronic devices.