Density Functional Theory Study of Metal-Organic Frameworks for Enhancement of Photo-Anode Properties

The optoelectronic properties of dye zinc and titanium-based metal-organic framework (MOF) compounds with regard to their application as photo-anode material characterized in solar cells were investigated. Analyses of the optoelectronic properties were performed on the MOF single crystal unit cell with adsorbed dye to determine the electronic and optical properties of the relevant materials. The electronic and optical properties were predicted by density functional theory (DFT) calculations. The results show that the absorption of light occurs for the examined MoF compounds from the near UV to the (visible) blue spectral range, at optical band gap sizes from 2.8 eV up to 3.88 eV. Dye sensitization of MOF with eosin Y or crown ether gave additive UV-Vis spectra. An improvement in band gap or an improved electron injection could be archived as well. Moreover, the light absorption does not solely depend on the linkers used, but also from the metal atoms in the secondary building unit. The fluorescence of MOFs depends on the linker and especially on the linker coordination and their rotation relative to each other. The utilizations of MOFs and their derivatives as electrodes, photoactive materials, charge carriers and additives in different solar cells are highlighted.