ZnS/CdX (X = S, Se, Te) core/shell nanowires: an attempt at tuning the electronic bandgaps and SQ efficiencies

Abstract

DFT based simulations were executed to investigate the electronic structures and a few optical constants of ZnS, CdS, CdSe and CdTe nanowires (NWs). It was observed that all these pristine...

Modulation of electronic bandgaps and subsequent implications on SQ efficiencies via strain engineering in ultrathin SnX (X = S, Se) nanowires

“…In comparison, a 33.59% SQ efficiency was reported by us in the case of ZnS/CdTe core/shell NWs. 75 Also, an SQ efficiency of up to 33.94% was reported in the case of a strained penta-PdSe 2 monolayer recently. 108 Even in the case of ultrathin SnS NWs, the SQ efficiency swells up to 29.28% at −10% compressive strain and up to 31.71% at +10% tensile strain.…”

“…Sufficient vacuums (≥10 Å) are introduced along the X - and Y -directions, with a view to keeping a check on the interactions amongst the adjoining NW images. 75 Fig. 1 shows the unstrained primitive cell of ultrathin SnX NWs.…”

“…This contraction in the bond angles, coupled with the slight elongation, in the case of SnSe NWs, hints towards a tad greater buckling height in the same. To gauge the stability of the ultrathin NWs, the formation energies are calculated using the formula: 75,85 where E SnX is the total energy of the fully optimized ultrathin SnX (X = S, Se) NW, E Sn is the free energy of the isolated Sn atom, E X is the free energy of the isolated X atom, m is the total number of Sn atoms, n is the total number of X atoms and N (= m + n ) is the total number of atoms in the ultrathin SnX NW. The formation energies for ultrathin SnS and SnSe NWs are −3.91 eV per atom and −3.58 eV per atom, respectively.…”

“…74 The growth direction of the ultrathin NWs was taken along the Z -direction, and sufficient vacuums (≥10 Å) were introduced along the X - and Y -directions to curb the interactions, among neighbouring NW images. 75 The conjugate gradient (CG) method was employed to optimize the primitive cells until the force on each atom was less than 0.001 Å per atom. 76 A 1 × 1 × 12 Monkhorst–Pack k -grid was chosen to sample the irreducible Brillouin zone.…”

“…Finally, the solar cell efficiency η can be determined using the formula: 80 where P in (∼1000 W m −2 ) is the aggregate incident power density, taken from the AM 1.5G solar irradiation spectrum. 75,80,83…”