Hexagonal boron nitride (h-BN) is a material of outstanding interest because of its exceptional properties and diverse applications across various fields, including electronics, optoelectronics, and quantum technologies.

Theoretical investigations of h-BN have involved advanced numerical methodologies, including the density functional theory (DFT), which allow us to computationally address material's properties, such as its thermal and electrical conductivity, stability, and electronic structure.

In particular, h-BN in its 2D monolayer form has emerged as a promising emitter of quantum light due to its optical, chemical, thermal, and fabrication properties. Its emission spectrum spans from ultraviolet to infrared wavelengths, making it a compelling subject for investigating photon emission properties toward applications in quantum computing, quantum crystallography, and quantum metrology.

An important aspect of material characterization involves understanding the role of defects in a crystalline structure. From a theoretical point of view, this is typically studied using the supercell method, which has a high computational cost, especially as the system complexity increases. To address these challenges, we explore an alternative approach which can achieve small substitutions using Virtual Crystal Approximation (VCA). By incorporating virtual atoms into DFT calculations, VCA provides results comparable to those obtained with the supercell method, but at a significantly reduced computational cost.

By combining VCA with the simple approach used to identify hydrogenoid defects, we obtain the band structure of slightly carbon-doped h-BN and determine how the monolayer emission can be significantly changed. This underscores the versatility of h-BN as a photon emitter for multiple applications, highlighting its importance in the current landscape of emerging quantum technologies.