Theoretical Study of a Novel WSi₂N₄/MoSi₂N₄ Heterostructure with Ultrafast Carrier Transport

Abstract

Promoting carrier separation and migration is the key factor to improve photocatalytic performance. In this work, we proposed a novel WSi 2 N 4 /MoSi 2 N 4 heterostructure including six different stacking configurations, in which the AB stacking configuration is thermodynamically most stable and can satisfy the requirement of overall water splitting. The presence of an internal electric field owing to the symmetry breaking will promote the carrier separation to different layers, and the low exciton (e−h pairs) binding energy (0.12 eV) and high carrier mobility further boost the separation and migration of electrons and holes; these results demonstrate that heterojunctions have high carrier activity and good photocatalytic performance. The high light absorption coefficient (∼10 5 cm −1 ) and enhanced visible light absorption also further support our theoretical predictions. Moreover, the research of nonadiabatic molecular dynamics provides a deeper understanding that the time of carrier transfer is much longer than e−h recombination (2420 fs for electrons, 67 ns for e−h recombination) and its intrinsic photocatalytic mechanism. These findings indicated that AB stacking with ultrafast carrier transport is an excellent photocatalyst.

Two-dimensional MX2Y4 systems: ultrahigh carrier transport and excellent hydrogen evolution reaction performances

“…65,66 HfSi 2 N 4 , MoSi 2 N 4 , TiSi 2 N 4 , WSi 2 N 4 , and ZrSi 2 N 4 show decent bandgaps (larger than 1.23 eV), leading to them being potential photocatalysts for water splitting, and some studies also proved their band edge positions to induce the hydrogen evolution reaction (HER) and oxygen evolution reaction. 67,68…”

“…65,66 HfSi 2 N 4 , MoSi 2 N 4 , TiSi 2 N 4 , WSi 2 N 4 , and ZrSi 2 N 4 show decent bandgaps (larger than 1.23 eV), leading to them being potential photocatalysts for water splitting, and some studies also proved their band edge positions to induce the hydrogen evolution reaction (HER) and oxygen evolution reaction. 67,68 The bandgaps of the MX 2 Y 4 monolayers imply their potential in photocatalytic and photovoltaic applications. The carrier mobilities in the MX 2 Y 4 monolayers are critical for such applications.…”

Tunable type-II lateral MoSi2N4/WSi2N4 heterostructures for photocatalytic applications

“…8 Suitable strains have been identified to trigger intriguing influences on the MoSi 2 N 4 monolayer and its van der Waals heterostructures. [51][52][53][54] Thus, we wonder if the strains will affect the type-II band alignment and direct-band nature in the (MoSi 2 N 4 ) 8 (WSi 2 N 4 ) 8 lateral heterostructure. Fig.…”

Theoretical Study of Superhigh-Efficiency Janus WSSe/β-Te Non-Perovskite Heterojunction Solar Cells

“…29 2D semiconductors belonging to the same system also have similar properties through the different stackings. 30 Although sliding at the van der Waals heterojunction interface has certain novel characteristics, its impact on the performance of 2D solar cells has not yet been thoroughly investigated. Additionally, one of the most efficient methods to regulate electronic structures is thought to be stress engineering.…”

“…Out-of-plane polarization is also produced by the specific stacking of bilayer MoSi 2 N 4 , which effectively separates photogenerated charges into different layers to improve optoelectronic efficiency . 2D semiconductors belonging to the same system also have similar properties through the different stackings . Although sliding at the van der Waals heterojunction interface has certain novel characteristics, its impact on the performance of 2D solar cells has not yet been thoroughly investigated.…”