Experimentally fabricated semiconducting ${\mathrm{Cu}}_2\mathrm{Se}$ monolayers with a high electron mobility of approximately ${10}^3{\mathrm{cm}}^2{\mathrm{V}}^{-1}{\mathrm{s}}^{-1}$ and exceptional environmental stability are promising for next-generation electronic device applications, such as field-effect transistors (FETs). However, the challenge of achieving Ohmic contacts with electrode metals persists. This study systematically investigates the interfacial properties of monolayer ${\mathrm{Cu}}_2\mathrm{Se}$-based transistors with various common metals ($\mathrm{Ti}$, $\mathrm{Mo}$, $\mathrm{Cr}$, $\mathrm{W}$, $\mathrm{Sb}$, $\mathrm{Cu}$, $\mathrm{Co}$, and $\mathrm{Ni}$) as electrodes, leveraging first-principles calculations and quantum transport simulations. Our findings reveal that metal-induced gap states enable ${\mathrm{Cu}}_2\mathrm{Se}$ to form Ohmic contacts with all metal electrodes except $\mathrm{Sb}$ in the vertical direction. Furthermore, the absence of a tunneling barrier results in high carrier injection efficiency in the ${\mathrm{Cu}}_2\mathrm{Se}/\mathrm{Ti}$, /$\mathrm{Mo}$, /$\mathrm{Cr}$, and /$\mathrm{W}$ interfaces. The strong Fermi level pinning effects confine the Schottky barrier of ${\mathrm{Cu}}_2\mathrm{Se}/$metal lateral contacts to a small value. Notably, ${\mathrm{Cu}}_2\mathrm{Se}/\mathrm{Mo}$ and ${\mathrm{Cu}}_2\mathrm{Se}/\mathrm{Cu}$ FETs demonstrate ideal Ohmic contacts in both vertical and lateral directions, with $\mathrm{Mo}$ electrodes exhibiting the highest contact quality in ${\mathrm{Cu}}_2\mathrm{Se}$-based FETs. The transfer behaviors of the ${\mathrm{Cu}}_2\mathrm{Se}/\mathrm{Mo}$ FETs nearly satisfy the standards in the International Technology Roadmap for Semiconductors for high-performance devices, aligning with the predicted quality of the electrode contacts. This work provides valuable theoretical guidance for the design of high-performance FETs utilizing ${\mathrm{Cu}}_2\mathrm{Se}$.

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• First-principles calculations
• Quantum transport
• Chalcogenides
• Field-effect transistors
• Monolayer films
• Schottky barriers
• Density functional calculations
• Nonequilibrium Green's function