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

Finding the material characteristics satisfying most of the photovoltaic conditions is difficult. In contrast, utilization of foreign materials that can contribute to light harvesting and charge transfers in the devices is now desirable/thought-provoking. Herein, a binary hybrid photoanode utilizing nano-amassed micron-sized mesoporous zinc oxide hollow spheres (meso-ZnO HS) in conjunction with SnO 2 nanoparticles (NPs), i.e., SnO 2 NP_ZnO HS (for an optimized weight ratio (8:2)), displayed a nearly ∼4-fold increase in the efficiency (η) compared to that of bare SnO 2 nanoparticle device. Enhanced device efficacy in the composite photoanode-based device can be accredited to the dual function of nano-amassed meso-ZnO HS. Nano-amassed micron-sized ZnO HS embedded in the photoanode can increase the light-harnessing capability without sacrificing the surface area as well as optical confinement of light by multiple reflections within its cavity and enhanced light-scattering effects. Electrochemical impedance spectroscopy analysis revealed an extended lifetime of electron (τ e ) and a higher value of R ct2 at the working electrode/dye/redox mediator interface, indicating a minimum photoinduced electron interception. The open-circuit voltage decay reveals a slower recombination kinetics of photogenerated electrons, supporting our claim that the nano-ammased meso-ZnO HS can serve as an energy barrier to the photoinjected electrons to retard the back-transfer to the electrolyte. Moreover, the improvement in the fill factors of the composite-based devices is endorsed to the facile penetration of the electrolyte through the pores of nano-amassed meso-ZnO HS, which increases the regeneration probability of oxidized dyes.

In this work, we have demonstrated an efficient and simple reusable catalyst, which can be operated on site for water remediation. In the present report, we have proposed a near 100% dye adsorption and the effective removal of arsenic­(III) using a ternary composite consisting of ORMOSIL-Fe3O4-RGO. A simple and low-temperature synthesis to prepare an ORMOSIL-Fe3O4-RGO composite has been developed as a one stop solution for water remediation. Particularly, this composite was employed for the elimination of arsenite (III) ions and Rhodamine B dye from water, which has a huge impact in developing/underdeveloped countries in South Asian and some of the American regions. The structural, physical, and chemical properties of this composite were investigated through various characterization techniques like powder X-ray diffraction (PXRD), fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), energy dispersion X-ray (EDS), transmission electron microscopy (TEM), and vibrating sample magnetometer (VSM). Using Langmuir isotherms, we calculated the adsorption capacity of the ORMOSIL-Fe3O4-RGO composite for Rhodamine B to be ∼1339 mg/g, which is much higher as compared to that of the Fe3O4-RGO composite (∼342 mg/g). Furthermore, the capacity of arsenic adsorption of this novel composite material is ∼25% higher than that of Fe3O4-RGO according to the Langmuir adsorption isotherm.

The light harvesting effects along with the energy barrier properties in dye sensitized solar cells (DSSCs) have been studied by utilizing an easily synthesizable and costeffective nanocube assembled micron-sized SrTiO 3 (STO NCMS) in a binary hybrid photoanode with ZnO nanoparticles. An optimized photoanode loaded with 3% STO NCMS yielded a ∼2-fold increment in power conversion efficiency compared to pristine ZnO NP based device. Improved performance of photoanode with hybrid composite scaffold can be accredited to the boosted optical response in conjunction with impeded reverse tunneling probability of STO NCMS containing photoanode. Micron-sized STO NCMS provides a better light absorption in the photoanodes owing to optical confinement of incident light by multiple reflections generated from mirror-like facets of SrTiO 3 nanocubes as well as enhanced light scattering effects from individual entity. IPCE analysis revealed a better absorption of low energy photons that in turn resulted in enhanced solar to electricity generation for an optimized ratio of STO NCMS. An effective photoinduced charge separation has been achieved with a uniquely aligned band structure, resulting in enhanced power conversion efficiency. Electrochemical impedance analysis unveiled that incorporation of STO NCMS can effectively prolong the lifetime of photo-injected electrons (τ e ) as well as a higher value of recombination resistance (R rec ) at the semiconductor/ dye/electrolyte heterointerface indicating an impeded reverse tunneling probability of photoinjected electrons.