of dyes . The reason behind this is that carbon materials like graphene and CNTs have a high work function, but the coupled semiconductors' or coupled dyes' CB is more negative than the work functions of graphene and CNTs, as shown in Figure , with a value of approximately -0.30 eV vs. NHE [150] and -0.08 eV vs. NHE , respectively. The collected electrons either build up on carbon materials' surfaces or move quickly to reactive locations throughout their conductive surfaces. Carbon materials also have a low specific weight, which is great for structural purposes.