2D materials are an emerging class of materials that have been developing in recent decades. Generally, 2D materials are crystalline materials that their crystalline order is limited in one direction. This confinement divides 2D materials into two main classes, including atomically 2D materials (such as graphene and BP) and extremely thin 2D materials (such as transition metal dichalcogenides, MXenes, and 2D-perovskites). Due to their special and individual properties, scientists believe that 2D materials will play an undeniable and extraordinary role in the future of industry and technology. Among these special properties, fabulous optoelectric properties of 2D materials such as anisotropic electrical properties, including appreciable absorption coefficient and conductivity in different directions, very high transparency, flexibility, lightweight, and even good mechanical strength, have led to various applications of these materials in photovoltaic devices including silicon, thin-film, perovskite, dye-sensitized, and multi-junction solar cells as charge transport layers, absorption layers, and contact layers. In this chapter, we will introduce some of the most famous families of 2D materials with their individual properties for utilization in different types of solar cells.