The electronic and optical properties of graphene and other 2D materials are highly sensitive to changes in their structural defects and doping levels. These properties can be significantly altered by introducing defects or dopants, which can be advantageous for various applications, such as electronics, optoelectronics, and sensing devices. Here, we discuss how these properties change with variations in structural defects and doping levels.1. Structural defects: Structural defects in graphene and 2D materials can be in the form of vacancies, dislocations, grain boundaries, or edges. These defects can act as scattering centers for charge carriers, leading to changes in the electronic properties.- Mobility: The presence of defects can reduce the mobility of charge carriers electrons and holes in the material, which can negatively impact the performance of electronic devices.- Bandgap: Defects can also induce localized states within the bandgap of 2D materials, which can lead to the opening of a bandgap in graphene or modifying the bandgap of other 2D materials. This can be useful for tuning the electronic and optical properties for specific applications.- Carrier concentration: Defects can act as charge traps, affecting the carrier concentration in the material. This can lead to changes in the electrical conductivity and the overall electronic behavior of the material.2. Doping level: Doping refers to the intentional introduction of impurities or foreign atoms into a material to modify its electronic properties. In the case of graphene and 2D materials, doping can be achieved by chemical, electrostatic, or substitutional methods.- Type of doping: Depending on the dopant used, the material can be either n-doped electron-rich or p-doped hole-rich , which can significantly affect the electronic properties, such as conductivity and carrier mobility.- Bandgap: Doping can also modify the bandgap of 2D materials, which can be useful for tuning their electronic and optical properties for specific applications. For example, the bandgap of transition metal dichalcogenides TMDCs can be tuned by doping, enabling their use in optoelectronic devices with desired wavelength response.- Optical properties: Doping can also affect the optical properties of 2D materials, such as absorption, reflectance, and photoluminescence. These changes can be exploited for various applications, such as solar cells, photodetectors, and light-emitting diodes LEDs .In summary, the electronic and optical properties of graphene and 2D materials can be significantly altered by introducing structural defects or modifying the doping level. Understanding and controlling these properties is crucial for the development of advanced electronic, optoelectronic, and sensing devices based on these materials.