Chemically Functionalized Penta-stanene Monolayers for Light Harvesting with High Carrier Mobility

Two pentagonal tin-based two-dimensional materials, penta-stanane (p-SnH) and fluorinated penta-stanane (p-SnHF), are theoretically predicted on the basis of the density functional theory calculations. Both the proposed monolayers are formed by virtue of some pentagonal Sn rings in which all of Sn atoms are sp3 hybridized to the four nearest adjacent Sn atoms. Interestingly, they have lower formation energy than the free-standing stanene that has been grown on a Bi2Te3(111) substrate. Moreover, they have significant prospects for high-efficiency light harvesting with optical band gaps (1.88 eV for p-SnHF and 2.02 eV for p-SnH) that closely match the solar light spectrum. In particular, the band edge of p-SnHF is properly aligned that enables the band gap to cover the redox potential of H+ and O2– ions for water splitting, whereas the band edge of p-SnH can be moved down to the desired level when a small tensile strain (<5%) is applied. Meanwhile, the high carrier mobility (up to 769 and 2520 cm2 V–1 s–1 f...