Yanming Lin

The phenomenon of intriguing Rashba spin splitting, which is driven by intrinsic structural symmetry breaking and spin-orbit coupling (SOC), has been observed in various perovskite materials. However, it remains unclear how phonon vibrational frequency affects spin carrier dynamics in two-dimensional perovskites exhibiting the Rashba effect. A thorough exploration of the electronic structures and the mechanism behind the strain-induced lattice vibration on spin dynamics in Ruddlesden-Popper (RP) Cs₂GeI₂Cl₂/InSe heterostructure is presented herein, based on nonadiabatic molecular dynamics (NAMD) simulations with spin-orbit coupling (SOC) and density functional theory. Remarkably, the bandgap magnitudes and the extent of spin splitting within the Cs₂GeI₂Cl₂/InSe heterostructure has been significantly increased under compressive strain (ε = -4%). This enhancement is attributed to the decrease of the in-plane Ge-Cl bond length, which results in stronger Coulomb interaction and increased distortion of the [GeI₂Cl₄]^4- octahedral. When applying compressive strain on the heterostructure, more high frequency phonons (200-1000 cm^-1) participate in carrier relaxation process, leading to ultrafast spin dynamics (310.01 fs). The frozen phonons NAMD results show that high-frequency phonons promote carrier transfer more than low-frequency phonons in the 2D perovskite-based heterostructure. Interestingly, the Rashba spin dynamics also can be manipulated by the temperature, revealing that the phonon vibrational frequency is temperature-dependent. These findings highlight the importance of high-frequency phonons on Rashba spin dynamics in perovskite-based photoelectronic devices.

This work theoretically studies the photovoltaic performance and carrier dynamics of S-scheme CsSnBr₃/SnS_x (x = 1, 2) heterostructures. The V_Br(6.3%)–CsSnBr₃/SnS-based solar cell device exhibits the highest power conversion efficiency (26.58%).

The physical mechanisms governing the photocatalytic behaviors of C‐ or Ti‐doped SnS₂ are investigated based on first‐principles calculations. The calculations reveal that C atoms prefer to occupy interstitial sites around the surface, whereas Ti atoms are more likely to occupy the Sn atom positions around the surface. C atoms that occupy the C_i−2 interstitial site around the surface and inside the bulk will result in an occupied shallow defect state above the valence band maximum (VBM). The electronic lifetimes excite by visible‐light irradiation at the conduction band minimum (CBM) will be prolonged due to different real‐space positions of electrons at the CBM and the holes at the defect state. Ti atoms that occupied the Sn atom positions in the inner bulk will introduce two local shallow unoccupied defect states below the CBM, which are electron traps and delay the return of excited electrons to the valence band. The lifetime of holes at the VBM will be prolonged, The theoretical explanations based on Shockley–Read–Hall recombination theory enable the photocatalytic behavior to be understood deeply under the theoretical framework of semiconductor physics.

The energy band alignment and photocatalytic performance of α‐In₂Se₃/g‐C₃N₄ heterojunctions of two configurations (A and B) are studied through first‐principles calculations. The spontaneous out‐of‐plane electric polarization of α‐In₂Se₃ points away from g‐C₃N₄ for configuration A, in which the layer spacing and formation energy are lower than those of configuration B. Configuration A of α‐In₂Se₃/g‐C₃N₄ is characteristic of the I‐type energy band alignment and S‐scheme heterojunction for photocatalytic performance, which is different from the II‐type band alignment characteristic of the previous traditional Z‐scheme heterojunctions with a larger built‐in electric field. The existence of a stronger intrinsic electric field of α‐In₂Se₃ causes the photogenerated electrons in α‐In₂Se₃ to migrate across the interface region of α‐In₂Se₃/g‐C₃N₄ to reach the valence band maximum (VBM) of g‐C₃N₄ for configuration A. The recombination of the photogenerated electrons from the conduction band minimum (CBM) of α‐In₂Se₃ with holes from the VBM of g‐C₃N₄ reduces the number of photogenerated holes in the VBM of g‐C₃N₄. The photogenerated electrons in the CBM of g‐C₃N₄ due to the absence of holes move toward the surface of g‐C₃N₄ and play a significant role in the hydrogen generation activity.

Anatase titanium dioxide (TiO2) has attracted much attention due to its excellent photocatalytic properties. However, the band gap of anatase TiO(2)( )is 3.2 eV, which can absorb only about 4% of the ultraviolet light (lambda < 400 nm). Molybdenum disulfide (MoS2) is a new layered two-dimensional compound semiconductor, and it has been widely studied for its preferably optical absorption and photocatalytic properties. Moreover, the high recombination rate of photoexcited electron-hole of monolayer MoS2 leads to low photocatalytic efficiency. In this work, based on Heyd-Scuseria-Ernzerhof (HSE06) hybrid density functional theory, the geometric structure, electronic structure, optical properties, charge transfer and effect of pressure on structure of Cu/N doped TiO2/MoS2 heterostructures are systematically studied. The interface interaction between anatase TiO2 (101) surface and monolayer MoS2 shows that TiO2 and MoS2 form a van der Waals heterostructure. The defect formation energy is calculated to demonstrate that Cu@O&N@O is the most stable codoping site. The result of the density of states shows that the band gap of TiO2/MoS2 heterojunction is 1.38 eV, which is obviously smaller than that of the pure anatase TiO2 (101) surface (2.90 eV). The band gap of Cu/N doped TiO2/MoS2 heterojunction obviously decreases, and an impurity band provided by Cu 3d orbitals appears in the forbidden band, which leads to the decrease of the photon excitation energy and the enhancement of the optical absorption capacity. The x-y planar averaged and three-dimensional charge density difference of Cu/N doped TiO2/MoS(2 )are also calculated. It is found that there are electrons' and holes' accumulation in the doped anatase TiO2 (101) surface and the single layer MoS2, showing that the Cu/N doping can effectively reduce the recombination of the photoexcited electron hole pairs. Calculated optical absorption spectra show that Cu/N doped TiO2/MoS(2 )system has obvious improvement in the absorption of visible light. In addition, we calculate the geometrical, electronic and optical absorption spectra of TiO2/MoS2 heterojunction under different pressures. The results show that the appropriate increase of pressure can effectively improve the optical absorption properties of heterojunction and Cu/N doped TiO2/MoS2 heterojunction and TiO2/MoS2 heterojunction can effectively improve the optical properties of the material. These findings are helpful in understanding the photocatalytic mechanism and relevant experimental observations.