Mimicking the properties of heteroleptic ruthenium dyes, a dipyrido[3,2-a:2′,3′-c]phenazine-11-carboxylic acid (dppz-COOH) ligand based homoleptic complex, Ru(dppz-COOH)2(NCS)2, with a molar extinction coefficient of 14.3 × 103 M–1 cm–1 has been demonstrated as an efficient photosensitizer for the one-dimensional (1D) ZnO nanowire (NW) and ZnO nanoparticle (NP) based dye-sensitized solar cells (DSSCs) employing cobalt complexes as the redox mediators. The as-synthesized homoleptic dye achieves an intense metal-to-ligand charge transfer (MLCT) absorption band throughout the visible region due to the optimal π-conjugated dipyridophenazine ring extension and concomitantly retains an efficient dye loading tendency as confirmed by the chemisorption results. Electron density distributions of the frontier molecular orbitals obtained from density functional theory (DFT) indicated a characteristic MLCT transitions of the dye molecule as well as a favorable charge transfer feasibility from the lowest unoccupied molecular orbital of the dye to the conduction band of ZnO through the anchoring carboxylic groups. All the fabricated DSSCs were characterized by measuring the current density–voltage, incident photon-to-current conversion efficiency, and the electrochemical impedance spectroscopy (EIS). The results establish an efficient light harvesting property of the dye and explain the significance of faster charge transport through 1D ZnO NWs in enhancing the device efficiency in contrast to its ZnO NP counterpart. In consort with the interfacial charge transfer and recombination processes occurring in the DSSCs, EIS analysis likewise provides an insight into the prolonged photoinduced electron lifetime for the cells composed of ZnO NWs as compared to ZnO NPs.

Favourable charge recombination kinetics are achieved to enhance solar hydrogen production utilizing reduced graphene oxide coated onto noble metal free CuBi2O4.

Harvesting clean energy from sunlight is a promising and desirable path to resolve the energy challenge through photoelectrochemical (PEC) water splitting. Herein, we report the design and synthesis of a stable hematite photoanode with sequential metal and nonmetal incorporation to resolve the limiting factors such as low carrier density and high charge recombination for its practical applications. Comprehensive morphological, optical, and photoelectrochemical properties of the doped hematite photoanodes are presented to understand the mechanisms by which the dopant incorporation impacts the photoelectrode performance. It is found that with controlled calcination temperature metal and nonmetal incorporation not only increases the carrier density but also facilitates faster charge transfer. The charge carrier density of the photoanode derived from Mott–Schottky plot shows an increase by an order of magnitude, i.e., from 5.1 × 1019 to 5.7 × 1020 cm–3, with dual modification. The dual modified hematite photoanode shows a photocurrent density of 2.56 mA/cm2 at 1.23 V vs RHE, which is ∼5-fold higher as compared to that of the bare hematite photoanode. We believe that the present method of designing and fabricating the hematite photoanode by sequential incorporation of metal and nonmetal will provide an economical and efficient strategy for better solar energy conversion.

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Noble metal-free counter electrode using a co-catalytic loading of MoS2 nanosheets to Cu2ZnSnS4 microspheres are investigated by means of CuInS2-CdSe quantum dot (QD) co-sensitized solar cells fabricated with single crystalline ZnO nanowires. An ex situ electrophoretic deposition route is employed to deposit QDs onto ZnO nanowires that are epitaxially grown on ZnO seed layered FTO substrates. Hydrothermally grown ZnO nanowires have also established an excellent stability against the bias conditions applied to fabricate the photoanodes of the devcies. The superior photovoltaic performance of CuInS2-CdSe QD co-sensitized cells are compared with that of bare CuInS2 and CdSe counterparts, using current-voltage and incident photon-to-current conversion efficiency measurements. The present study also demonstrates an enhanced performance of the devices fabricated with 1.0 wt % of MoS2 loaded Cu2ZnSnS4 basaed counter electrodes in contrast to bare Cu2ZnSnS4. Hydrothermal loading of MoS2 to Cu2ZnSnS4 generates an electrically interconnected network of Cu2ZnSnS4 microspheres, leading to a facile charge transport in the counter electrode of the devices. MoS2 in its nanosheet form acts as an electrical bridge that interlinks the Cu2ZnSnS4 microspheres. Additionally, a favorable band energy alignment of Cu2ZnSnS4 and MoS2 stimulates the charge transfer dynamics in Cu2ZnSnS4-MoS2 composite. Electron transport and recombination kinetics of the devices are measured using electrochemical impedance spectroscopy.devices revealed an additional benefit of direct 1D electrical