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a Efficient charge separations and their mobility is a key challenge in metal-organic-frameworks (MOFs) based devices. In the present study, thin films of cobalt-based metal organic frameworks (MOFs) are synthesized using layer-by-layer technique, and their electrical/optoelectronic properties are studied. The as-prepared MOF films show electrically insulating behavior, which after hole doping demonstrate p-type conducting material. The measured HOMO-LUMO energy states of the MOF films are found to be well matched for sensitizing TiO2, and the photoluminescence quenching experiment demonstrates a facile photoelectron transfer path from the doped frameworks to TiO2. Consequently, the doped MOFs are employed successfully as a light harvesting and charge transporting active layer in a fully devised TiO2based solar cell. Two different organic ligands viz., benzene dicarboxylic acid, and naphthalenedicarboxylic acid are used to synthesize two kinds of Co-MOFs having different geometrical dimensions of unit cells and pores, and their influence on hole doping and charge transportation are studied. Under an optimized condition, the Co-MOF based device demonstrates the solar-to-electric energy conversion efficiency of 1.12 % with short circuit current of 2.56 mA.cm -2 , showing a promissing future prosprect on application of Co-MOFs in photovoltaics. Further, the photovoltaic performance of the Co-MOF based divice is comaparatively studied with the previously reported Cu-MOF and Ru-MOF based similar devices, and the influence of different metal centers to MOFs on their light harvesting performce is discussed.

This work reports on designing of first successful MOF-sensitizer based solid-state photovoltaic device, perticularly with a meaningful output power conversion efficiency. In this study, an intrinsically conductive cobalt-based MOFs (Co-DAPV) formed by the coordination between Co (II) ions and a redox active di(3-diaminopropyl)-viologen (i.e., DAPV) ligand is investigated as sensitizer. Hall-effect measurement shows p-type conductivity of the Co-DAPV film with hole mobility of 0.017 cm V s, suggesting its potential application as hole transporting sensitizer. Further, the energy levels of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of Co-DAPV are well-matched to be suitably employed for sensitizing TiO. Thus, by layer-by-layer deposition of hole conducting MOF-sensitizer onto mesoporous TiO film, a power conversion efficiency of as high as 2.1% is achieved, which exceeds the highest efficiency values of MOF-sensitized liquid-junction solar cells reported so far.

In the present work, TiO2 nanoparticle and multi-walled carbon nanotubes composite powder is prepared hydrothermally. After doctor blading the paste from composite powder, the resulted composite film is sensitized with Cu-based metal-organic frameworks using a layer-by-layer deposition technique and the film is characterized using FE-SEM, EDX, XRD, UV/Visible spectrophotometry and photoluminescence spectroscopy. The influence of the carbon nanotubes in photovoltaic performance is studied by constructing a Grätzel cell with I3−/I− redox couple containing electrolyte. The results demonstrate that the introduction of carbon nanotubes accelerates the electron transfer, and thereby enhances the photovoltaic performance of the cell with a nearly 60% increment in power conversion efficiency.