Abstract
Layered graphitic materials exhibit new intriguing electronic structure and the search for new types of two-dimensional (2D) monolayer is of importance for the fabrication of next generation miniature electronic and optoelectronic devices. By means of density functional theory (DFT) computations, we investigated in detail the structural, electronic, mechanical and optical properties of the single-layer bismuth iodide (BiI3) nanosheet. Monolayer BiI3 is dynamically stable as confirmed by the computed phonon spectrum. The cleavage energy (Ecl) and interlayer coupling strength of bulk BiI3 are comparable to the experimental values of graphite, which indicates that the exfoliation of BiI3 is highly feasible. The obtained stress-strain curve shows that the BiI3 nanosheet is a brittle material with a breaking strain of 13%. The BiI3 monolayer has an indirect band gap of 1.57 eV with spin orbit coupling (SOC), indicating its potential application for solar cells. Furthermore, the band gap of BiI3 monolayer can be modulated by biaxial strain. Most interestingly, interfacing electrically active graphene with monolayer BiI3 nanosheet leads to enhanced light absorption compared to that in pure monolayer BiI3 nanosheet, highlighting its great potential applications in photonics and photovoltaic solar cells.
Highlights
Layered graphitic materials exhibit new intriguing electronic structure and the search for new types of two-dimensional (2D) monolayer is of importance for the fabrication of generation miniature electronic and optoelectronic devices
Using particle swarm optimization (PSO), Li et al discovered a novel 2D inorganic material, namely Be2C monolayer, in which each carbon atom binds to six Be atoms in an almost planar fashion, forming a quasi-planar hexa-coordinate carbon moiety[20]; Tan et al predicted that the BSi3 silicene containing planar cyclic six-membered silicon rings (c-BSi3) is the global minimum of BSi3 monolayer[21]
We find that the spin orbit coupling (SOC) is significant and can reduce bandgap by around 1.0 eV in monolayer BiI3 nanosheet
Summary
All the calculations were performed employing the generalized gradient approximation in the Perdew-Burke-Ernzerhof form (GGA-PBE)[44] and the projector augment wave method[45,46], as implemented in Viena ab intio simulation package (VASP)[47,48]. 400 eV for geometry optimization and to 500 for static electronic structure and optical property computations. All the geometry structures were fully relaxed until energy and force were converged to 1E−5 eV and 0.005 eV/Å, respectively. Unit cell of BiI3 (containing 8 atoms) with 5 × 5 × 1, 9 × 9 × 1 and 17 × 17 × 1 Monkhorst− Pack k-point sampling were used for BiI3 monolayer geometry optimization, static electronic structure and optical property calculations, respectively. An increased plane wave energy cutoff of 500 eV and an 11 × 11 × 1 k-point sampling were employed, accompanying with more stringent convergence criteria. The k-point mesh used for geometry optimization and static calculation was 5 × 5 and 15 × 15, respectively. A large number of empty (conduction band) states are included for the summation in the equation
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