This paper presents a model to understand the efficiency of defect-based quantum emitters, focusing on the role of electron-phonon coupling. Single-photon emitters are crucial for quantum networks, and defects in semiconductors are promising platforms. The model shows that nonradiative processes dominate at lower photon energies, reducing efficiency. Reducing phonon frequency can enhance efficiency. The paper evaluates approximations used in the literature and discusses the impact of electron-phonon coupling on emission rates. It highlights the importance of minimizing nonradiative decay and suggests reducing phonon frequencies to improve efficiency. The study also discusses the role of spin and charge dynamics in emitter efficiency. Examples of known emitters, such as the NV and SiV centers in diamond, are analyzed. The paper concludes that efficient emitters are challenging to achieve at telecom wavelengths, but cavity coupling and quantum frequency conversion can help. The optimal single-photon emitter is yet to be discovered, but efforts to reduce phonon frequencies and optimize defect properties are promising. The study emphasizes the need for further research to identify the most efficient emitters.This paper presents a model to understand the efficiency of defect-based quantum emitters, focusing on the role of electron-phonon coupling. Single-photon emitters are crucial for quantum networks, and defects in semiconductors are promising platforms. The model shows that nonradiative processes dominate at lower photon energies, reducing efficiency. Reducing phonon frequency can enhance efficiency. The paper evaluates approximations used in the literature and discusses the impact of electron-phonon coupling on emission rates. It highlights the importance of minimizing nonradiative decay and suggests reducing phonon frequencies to improve efficiency. The study also discusses the role of spin and charge dynamics in emitter efficiency. Examples of known emitters, such as the NV and SiV centers in diamond, are analyzed. The paper concludes that efficient emitters are challenging to achieve at telecom wavelengths, but cavity coupling and quantum frequency conversion can help. The optimal single-photon emitter is yet to be discovered, but efforts to reduce phonon frequencies and optimize defect properties are promising. The study emphasizes the need for further research to identify the most efficient emitters.