Resolving the Anisotropic Dynamical Evolution of Wide Bandgap GeSe₂ Under Polarized Photoexcitation

Germanium diselenide (GeSe₂) has recently emerged as a promising material for high-performance optoelectronic devices due to its high absorption coefficient, wide direct bandgap, and anisotropic electronic properties. For the future applications, it is necessary to understand the dynamic evolution of carriers with ultrafast response. In this work, the transient absorption spectroscopy measurements are performed to study the anisotropic dynamic evolution of GeSe₂ under the polarized photoexcitation. It is find that the dynamics exhibit linear dichroism and show a significant Auger recombination process when the photoexcitation is perpendicular to the b-axis of GeSe₂. Using first-principle and transition dipole moment calculations, it is confirmed that the more carrier localization at Γ point along the Γ-X (perpendicular to the b-axis) and increase the Auger recombination. In addition, the Auger recombination coefficient ≈ 1.1×10⁻³¹ cm⁶ s⁻¹ is determined and demonstrated that the defect-assisted indirect Auger recombination plays a key role in the carrier relaxation process. Through time-resolved transient absorption spectra, it is further revealed that the ultrafast dynamical evolution of excited state absorption peaks under polarized photoexcitation. These results have implications for improving the quantum efficiency of high-field polarization-sensitive optoelectronics.