• Energy Research

An overview of the advantages and challenges of photocatalytic water splitting is provided to encourage new research directions mainly on data reproducibility and photocatalyst scalability.

Hydrogen is a most desirable solar energy storage medium. It provides reliable, scalable, and long-term energy storage, while helping in the decarbonization of the energy cycle. Such a storage medium is required for further deployment of photovoltaics, either for their inclusion into transportation and heavy industries or for supporting renewable grid management. The most accessible hydrogen source is water. However, fresh water is a scarce resource, while seawater is abundant worldwide. A major drawback of seawater electrolysis comes from chloride oxidation competing with the oxygen evolution reaction (OER). This may produce toxic products such as chlorine and also limits the hydrogen energy efficiency of the overall process. Thus, selective catalysts toward the OER are of strong technological interest. Here we report the electrocatalytic activity of heterogeneous cobalt hexacyanoferrate toward seawater oxidation. Combining experimental and computational studies, we highlight the great difficulty in obtaining such selectivity and its main mechanistic descriptors. This Prussian blue derivative is an excellent and robust OER electrocatalyst, but unfortunately, it is not selective enough toward the OER in the presence of Cl – anions. Faradaic efficiencies above 30% toward Cl 2 were observed during untreated seawater bulk electrolysis.

We describe the use of citric acid as co-adsorbent in Dye Solar Cells (DSC). As we demonstrate herein, it is possible to increase the photocurrent of DSC without loosing photovoltage when we employed cis-dithiocyanato(4,4′-dicarboxy-2,2′-bipyridine)(1,10-phenanthroline) ruthenium (II) (AR20). Moreover, we show that the dye molecular structure also plays a major role due to its interaction with the sensitizer.

Six organic dyes have been synthesized and used for the preparation of highly efficient and stable DSSCs. The implementation of one of them in a solar module with a large active area of 1400 cm2 is also presented.

AbstractA detailed account of the limiting factors of solvent‐annealed bulk‐heterojunction small‐molecule organic solar cells is given. This account is based on the extensive characterisation of solar cell devices made from a library of five diketopyrolopyrole (DPP) donor dyes. Their chemical structure is designed in such a way as to provide insights into the energetics of solar cell active layer micro‐structure formation. Numerous chemical and physical properties of the active layers are assessed and inter‐related such as light absorption, molecular packing in the solid state, crystal‐forming properties in thin films, charge carrier mobility and charge carrier recombination kinetics. A myriad of characterisation techniques are used such as UV/Vis absorption spectroscopy, photoluminescence spectroscopy, XRD, AFM and photo‐induced transient measurements, which provide information on the optical properties of the active layers, morphology and recombination kinetics. Consequently, a mechanism for the solvent‐vapour‐annealing‐assisted formation of crystalline domains of donor molecules in the active layer is proposed, and the micro‐structural features are related to the J–V characteristics of the devices. According to this model, the crystalline phase in which the donor crystallise in the active layer is the key determinant to direct the formation of the micro‐structure.

In this work, we assess the possible reasons for the differences observed in open circuit voltage (VOC) in mixed cation perovskite solar cells when comparing four different hole transport materials (HTMs), namely TAE-1, TAE-3, TAE-4 and spiro-OMeTAD.

The characterization of the interfacial charge transfer processes taking place in dye solar cells made using the most efficient ruthenium complexes, namely cis-bis(isothiocyanato)bis(2,2′-bipyridyl-4,4′-dicarboxylato)-ruthenium(II)bis-tetrabutylammonium (N719), tris(isothiocyanato)-ruthenium(II)-2,2′:6′,2′′-terpyridine-4,4′,4′′- tricarboxylic acid, tris-tertrabutylammonium salt (Black Dye) and cis-bis(isothiocanate)(4,4′-bis(5-hexylthiophene-2-yl)-2,2′-bipyridine)(4-carboxylic acid-4′-carboxylate-2,2′-bipyridine)ruthenium(II) sodium (C101), has been carried out. The comparison between these devices shows that devices made using N719 have the slowest recombination dynamics between the photo-injected electrons and the oxidized electrolyte. Moreover, for devices made using Black Dye, the dye ground state regeneration dynamics are faster than for C101 and N719. The implications for future ruthenium dyes are discussed.