Al<sub>2</sub>B<sub>12</sub>C with High Ambipolar\nMobility Driven by a Unique B–C Framework

The development of materials with\nhigh ambipolar mobility is pivotal\nfor advancing multifunctional applications, yet such materials remain\nscarce. Presently, cubic boron arsenide (BAs) stands out as the premier\nambipolar material, demonstrating an ambipolar mobility of ∼1600\ncm<sup>2</sup> V<sup>–1</sup> s<sup>–1</sup> at room\ntemperature [<i>Science</i> 2022, 377, 433 and <i>Science</i> 2022, 377, 437]. Herein, we illustrate that semiconducting Al<sub>2</sub>B<sub>12</sub>C, featuring a nonclathrate B–C framework\nin which a C atom bonds to the vertices of four distorted hexagonal\nantiprism B<sub>12</sub> units via quasi-sp<sup>3</sup> hybridization,\nis predicted to possess ambipolar carrier transport behavior. Its\nambipolar mobility can reach up to ∼2095 cm<sup>2</sup> V<sup>–1</sup> s<sup>–1</sup>. The hole transport originates\nfrom the C p<sub><i>z</i></sub> orbitals that trap the electrons\nof Al atoms at the valence band maximum, forming a C–Al–C\nhole channel along the <i>c</i>-axis direction, whereas\nelectron transport stems from the π electrons in B<sub>12</sub> units. For Al<sub>2</sub>B<sub>12</sub>C, polar optical phonon scattering\nserves as the primary mechanism limiting mobility. Additionally, it\ndisplays a high absorption coefficient (10<sup>5</sup> cm<sup>–1</sup>) in the visible spectrum. These appealing properties make Al<sub>2</sub>B<sub>12</sub>C a highly promising environmentally friendly\nsemiconductor for applications in electronics and photovoltaic devices.