Borophene Quantum Dots: A Sustainable Platform for PolarizationSensitive Infrared Photodetectors

Two-dimensional borophene is renowned for its exceptional metallicity and high electrical conductance. However, realizing its full potential in electronic and optoelectronic devices is hindered by the fundamental challenge of bandgap engineering. Although boron quantum dots (QDs) derived from bulk boron phases have shown promise in this regard, the existence, stability, and properties of genuine planar borophene fragments—borophene QDs—remain largely unexplored. To address this gap, we develop an edge-encoding strategy combined with a machine learning model to generate an extensive library of low-energy borophene QDs with diverse sizes, shapes, and edge configurations. These QDs exhibit high thermodynamic stability, narrow energy gaps, and nearly-degenerate singlet and triplet ground states—a consequence of their unique multicenter bonding and electron delocalization nature. The intrinsic spin polarization enables strong interactions with long-wavelength infrared (LWIR) photons and leads to distinct magnetic circular dichroism responses depending on spin multiplicity. Our results establish borophene QDs as a promising class of sustainable quantum materials for highly integrated, spin-active, and spectrally selective infrared photodetectors.