Two-dimensional (2D) materials with engineered electronic correlations are emerging as versatile platforms for next-generation optoelectronics. Here we present a comprehensive theoretical investigation of the electronic and optical properties of a C3N monolayer using a tight-binding framework combined with the Hubbard Hamiltonian and Green’s function formalism. We show that electron–electron interactions, mechanical strain, and carrier doping act as powerful tuning parameters that reshape the optical response. Coulomb correlations drive notable modifications in the density of states (DOS), giving rise to semi-metallic behavior under specific regimes. Optical conductivity calculations reveal a prominent absorption feature near 4 eV, which undergoes systematic blue shifts and intensity modulation upon electron doping, reflecting Fermi-level–controlled interband transitions. External strain further tailors both the spectral position and strength of optical excitations, establishing strain engineering as an effective control knob. Transmission and reflectivity spectra indicate broadband opacity of C3N, underscoring its potential for reflective coatings and nanoscale energy-control applications. Our results provide fundamental insights into the interplay of correlations, strain, and doping in 2D C3N, and establish design principles for tailoring its optoelectronic functionality in advanced device technologies.
