Assessing the role of plasma-engineered acceptor-like intra- and inter-grain boundaries of heterogeneous WS₂–WO₃ nanosheets for photocurrent characteristics

Abstract

High-temperature annealing in tungsten disulfide resulted in heterogeneous WS 2 -WO 3 in which intra-(within WS 2 and WO 3 ) and inter-(between WS 2 and WO 3 ) grain boundaries were observed, which were highly critical for charge transport and recombination. The heterogeneous WS 2 -WO 3 phase was evidenced by observing the coexistence of d-spacing values of 0.26 nm (WS 2 ) and 0.37 nm (WO 3 ) in transmission electron microscopic (TEM) studies. Further systematic high-resolution TEM studies elucidated that intra-grain boundaries separated crystallites within WS 2 and WO 3 , while inter-grain boundaries separated WS 2 from WO 3 . As WS 2 and WO 3 are both n-type, these defects are acceptor-like in the grain boundaries and they actively participate in the capture (trapping) process, which impedes charge transport characteristics in the heterogeneous WS 2 -WO 3 films. Plasma treatment in the heterogeneous WS 2 -WO 3 film, for 60 minutes using argon, energetically modulated the defects in the intra/ inter-grain boundaries, as evidenced from detailed comparative photocurrent characteristics obtained individually in (i) pristine WS 2 , (ii) heterogeneous WS 2 -WO 3 and (iii) Ar plasma-treated heterogeneous WS 2 -WO 3 films under blue and green lasers, along with AM1.5 (1 sun) illumination. Detrimental roles (trapping/de-trapping and scattering) of grain boundary states on photoelectrons were seen to be significantly suppressed under the influence of plasma.

Hydrothermal synthesis and controlled growth of group-VIB W metal compound nanostructures from tungsten oxide to tungsten disulphide

“…However, it has to pass through the structurally disordered inter-grain boundary, which affect the band structure by creating potential barriers. 65,66 Fig. 7(a i and a ii ) shows the calculated energy band structure, the TDOS and PDOS of the WO 3(5:1) -240 °C primitive-cell.…”

“…However, it has to pass through the structurally disordered inter-grain boundary, which affect the band structure by creating potential barriers. 65,66…”

Imperfect makes perfect: defect engineering of photoelectrodes towards efficient photoelectrochemical water splitting

“…80 For instance, CdTe photoanodes were annealed to increase the grain size and reduce the grain boundary density, leading to more efficient charge separation. 78 Grain boundaries exist in heterojunctions composed of two semiconductors, such as α-Fe 2 O 3 –SnO 2 , 81 WS 2 –WO 3 , 82 etc.…”

“…So far, many photoelectrode materials have been widely studied, such as TiO 2 , 117 ZnO, 39 α-Fe 2 O 3 , 143 WO 3 , 82 BiVO 4 , 118 SrTiO 3 , 38 g-C 3 N 4 , 121 TaON 144 and Ta 3 N 5 . 145 At the initial stage of PEC water splitting, research efforts are mainly concentrated on TiO 2 .…”

Magnetic, Electronic, and Optical Studies of Gd-Doped WO3: A First Principle Study

“…Especially, the photocatalytic activities and SGS properties of WO 3 can be modified by doping transitional elements such as Au, Pd, and Pt. Rare earth and transition metal-doped WO 3 systems show interesting magnetic properties that usually do not exist in undoped WO 3 [ 8 , 9 , 10 ]. In this study, the magnetic, electronic, and optical properties of Gd-doped WO 3 are investigated by using first principle calculations.…”