Understanding interlayer charge dynamics in van der Waals heterostructures is vital for advancing optoelectronic applications. The photogenerated carrier dynamics in two-dimensional $g\text{−}{\mathrm{C}}_3{\mathrm{N}}_4/\mathrm{MoS}{\mathrm{i}}_2{\mathrm{N}}_4$ are systematically explored via nonadiabatic molecular dynamics simulations and first‐principles calculations. It is found that the heterostructure exhibits a type‐II band alignment with a direct band gap of 1.88 eV with enhanced visible light absorption and high carrier mobility. Photoexcited electrons oscillate between layers with an insufficient transfer, and 69% of holes localize on $g\text{−}{\mathrm{C}}_3{\mathrm{N}}_4$ within 32 fs. Applying an external electric field of +0.1 V/Å significantly facilitates charge spatial separation; nearly 73% of electrons transfer to $\mathrm{MoS}{\mathrm{i}}_2{\mathrm{N}}_4$ layer within 223 fs and 96% of holes localize on $g\text{−}{\mathrm{C}}_3{\mathrm{N}}_4$ layer within 47 fs. This can be ascribed to the stronger electron‐phonon coupling, dominated by the excitation of the $A_2^{{}^{\prime }3}$ mode at 1034 $\mathrm{c}{\mathrm{m}}^{-1}$. Meanwhile, introducing the external electric field of +0.1 V/Å weakens nonadiabatic couplings and accelerates decoherence, thereby prolonging the electron‐hole recombination time to 28 ns. These findings highlight the role of an external electric field in optimizing interlayer charge dynamics of two‐dimensional heterostructures for high‐performance optoelectronics.

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• Charge dynamics
• Electron-phonon coupling
• Electronic structure
• 2-dimensional systems
• Interfaces
• Density functional theory
• Molecular dynamics