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A core-shell nano-heterostructured perovskite BiFO3@nitrogen doped mesoporous TiO2 (BFO/n-TiO2) hydrothermally assembled via using citric acid and polyethlene glycol (PEG) was characterized through XRD, TEM, FTIR, UV–Vis diffuse reflectance, IPCE, N2 adsorption and impedance spectroscopy. It has been demonstrated that the photovoltaic yield of the 90%N-TiO2-10%BFO electrode achieves a power conversion efficiency (PCE) of 4.5%, which is 1.85, 2.5, 3 and 1202 times higher than those of 10%N-TiO2-90%BFO, 50%N-TiO2-50%BFO, n-TiO2 and pristine BFO, respectively. It is acknowledged that the former electrode exhibits a significant visible light harvesting capability, lowest band gap (Eg = 2.0 eV) as well as the highest IPCE% (36% at 460 nm) values. The EIS and capacitance results illustrated that 90%N-TiO2-10%BFO owns excessive charge carriers (e− − h+); compared to rest of nanocomposites, with a great sparation, to assist boosting the PCE value. This was highly aided by the surface defects seen on the core represented by BFO, which worked as a rational carrier trapper between the N719 dye and the n-TiO2 shell structure. The surface texturing properties of the nanocomposite forming the 90%N-TiO2-10%BFO electrode including SBET (Asahi et al., 2001) and pore volume (0.48 cm3 g−1) have shared significantly in improving the conversion efficiency of such p-n heterojunction based solar cells; which never achieved as such in all BFO-based solar cell devices, with acceptable tunability. Keywords: BFO/n-TiO2, Core-shell structure, DSSC, Charge transfer, Heterojunction p-n, Surface defects

Nanocomposites of hexagonal ZnO nanorods incorporated into carbon nanotube-graphene (ZnO/CNT-GO) were prepared using a simple hydrothermal approach. The structure, light absorption, surface texturing, and morphology characterizations have established the strong interaction between ZnO, carbon nanotubes, and graphene oxide components because of the presence of well-dispersed ZnO nanorods with an aspect ratio of 3.4 (L × D = 75 × 22 nm). The assembled dye-sensitized solar cell of a ZnO/CNT-GO photoanode exhibited a superior performance, with a power conversion efficiency of 7.73%, surpassing those of its ZnO/CNT (5.07%) and ZnO/GO (3.96%) counterparts. Although CNT-GO exhibited a higher incident photon-to-current conversion efficiency (IPCE) and lower photoluminescence (PL) intensity than those of the ZnO/CNT-GO composite, it presented a lower conversion efficiency of 5.60%. This can be attributed to the presence of structural defects at the CNT/GO interface, which resulted in lower electronic conductivity (0.25 × 10−3 Ω−1 cm−1 vs. 0.8 × 10−3 Ω−1 cm−1 for ZnO/CNT-GO) and optical performance. The ZnO/CNT-GO composite showed a superior Isc value of 17.6 mA/cm2 but a lower Voc value of 0.63 V in comparison to those of its ZnO/GO analog (3.9 mA/cm2, 0.8 V); it also showed a manifested increase in surface area and pore radius values (227.5 m2/g, 58.9 A) toward the dye absorption. The electrochemical capacitance performance obtained via using charge-discharge and impedance spectroscopy revealed an excellent specific capacitance in the order of ZnO/CNT-G (290 F/g) > CNT-G (275 F/g) > ZnO/G (230 F/g) > ZnO/CNT (183 F/g) at 1.0 A g−1. This is attributed to the synergistic effect of ZnO within the CNT/GO nanocomposite and affirms its charge collection efficiency toward the improvement of dye-sensitized solar cells. The formation of a p/n junction between CNT/G and ZnO nanorods, as evidenced by the Mott-Schottky analysis, played a vital role in the improvement of solar cell devices based on the narrowing of the band gap (Eg = 2.64 eV), ease of electronic transfer, transient photocurrent density, as well as framework mesoporosity.

It is imperative to transform the sub-bandgap photons into higher energy photons that can significantly enhance the efficiency of the photovoltaic device. Upconverting nanoparticles (UCNPs), combine (sub-bandgap) photons to give high-energy photons. Hexagonal UCNPs of β-NaYF4 concurred with Yb3+ and Er3+ were prepared via thermal decay of metals trifluoroacetate precursors. A solvothermal method was used for the preparation of Ru3-(BTC)2 MOF. The precursors were mixed in a molar ratio 3RuCl3xH2O: 2H3btc:5CH3COOH: 925H2O. The prepared materials were characterized by X-ray diffraction, SEM, TEM, UV–V is absorption, and emission spectra. The solar cell ZnO/MOF/UCNPs Electrode was prepared by the deposition of MOF on the ZnO electrode by the spin coating method and annealed at 200 °C for 2 h. Then this electrode was immersed into 40 mM UCNPs for 24 h then heated to 400 °C to form a compact layer of UCNPs. The impact of β-NaYF4:Yb3+, Er3+ UCNPs on the performance of ZnO/MOF photoelectrode was studied through solar cell assembly in a sandwich structure. The results showed that the UCNPs-based MOF-solar cell exhibited a 15.6% increase in the photocurrent and a 22% increase in the power conversion efficiency compared with MOF sensitized solar cell (MOFSSC) without UCNPs. This enhancement could be due to the presence of the UCNPs that extends the spectral response range of MOF-SSC to the NIR region. So integrating up-converting materials into MOF-sensitized solar cells would generate a new kind of highly efficient solar cells that realize the utilization of the solar light energy in a broad spectrum from the UV to the NIR region.

Mn3O4 (M) incorporated graphenes (G) synthesized by a deposition–solvothermal process, formed at various nominal weight percentages (G1M1, G3M1 and G1M3), were efficiently used for the photodegradation of methylene blue dye (MB) under visible light illumination (λ > 420 nm, 88 W, 20 ppm, 298 K) and under microwave irradiation (800 W, 2.45 GHz, 373 K). These materials were characterized using XRD, TEM-SAED, UV-Vis diffuse reflectance, N2 sorptiometry, FTIR and Raman techniques. Amongst the nanocomposites, G3M1 of polyhedral structure and an average domain equal to 10–12 nm has presented unique photo-degradation performance (100% degradation, 60 min, 0.0791 min−1 and TOC of 60%) exceeding the rest of the materials. This was mainly due to the extraordinary optical properties and to the strong interaction between Mn3O4 and graphene through which charge recombination is hampered. Based on the conduction and valence band edges together with the studied reactive species, it has been shown that ˙OH was the dominant species responsible for the MB degradation. Interestingly, the G3M1 nanocomposite has shown fascinating microwave absorption properties and is capable of degrading MB at a faster rate (0.287 min−1) than the one conducted via photocatalysis. Scavenger studies have shown that ˙OH and electrons were responsible for the excellent performance of the MB microwave degradation. The microwave results were discussed in view of the marked increase in dielectric constant (e−) and dielectric loss (e′′) in the studied frequency range of 1.0 Hz to 100 kHz, in addition to the electronic conductivity measurements. This work offers an exceptional approach for exploring high-performance microwave absorption as well as distinctive visible light photocatalytic reaction for organics degradation.

This work investigated the influence of the organic dyes Orange IV and Eosin Y as photosensitizers on the photovoltaic parameters of ZnO photoelectrode dye-sensitized solar cells (DSSCs). ZnO was prepared by homemade ZnO nanoparticles. X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and BET measurements were used to characterize the structures and the morphology of ZnO nanostructures. The Orange IV demonstrated the best performance compared with the cell sensitized with the Eosin Y. This occurred as Orange IV demonstrated the highest molar extinction coefficient.

Spherical TiO2 particles (60 nm) were obtained by using a Triton X-100. The surfactant was employed in two stages, i.e., in the hydrolysis of TiCl4 and then in the precipitation of the corresponding Ti (IV) polymers. The advantages of such spherical TiO2 particles were examined in terms of photovoltaic characteristics of a dye-sensitized solar cell (DSSC) using Orange IV dye as sensitizer. Significantly higher overall solar energy conversion efficiency was obtained for a DSSC using the film of these spherical TiO2 particles, compared with that of a cell using a TiO2 film prepared without surfactant.

Current researches had shown that the electrical conductivity of most polymers depend on the method of its preparation and type of fillers. This research therefore aimed at studying the electrical properties of polyaniline carbon nanotubes nanocomposite prepared by hand mixing and decoration methods. The effect of preparation method on electrical properties of polyaniline containing Carbon Nanotubes (CNTs) and silver nanoparticles was studied. The formation of Ag NPs was confirmed by XRD. The AC-conductivity, dielectric permittivity (e’) and dielectric loss (e’’) of (CNTs/PANI/Ag) nanocomposites have been measured in the temperature range from 298 to 433 K and frequency range from 10 to 100 kHz. The Ag-CNTs improved the electrical conductivity and dielectric properties of polyaniline. The electrical conductivity of the CNTs/Ag/PANI nanocomposite prepared by decoration method is higher than composites prepared by mixing method.

ZnO and Fe2O3 nanoparticles have been formed in a silica matrix, through the sol–gel method and were used as a photoanode to fabricate dye-sensitized solar cells (DSCs). The obtained oxides were characterized by X-ray diffraction, infrared spectroscopy, scanning electron microscope and UV–visible absorption spectroscopy. The results indicate that ZnO and Fe2O3 prepared by this method may be used as photoanodes in photo-electro-chemical energy conversion systems. DSSCs have been built using eosin Y as photosensitizer and their photocurrent, open-circuit voltage, fill factor and efficiency have been measured under direct sunlight illumination (1000 Wcm−2). A ZnO-film solar cell had the best performance with an open-circuit voltage of Voc=0.7 V and short-circuit current density of Isc=490 μA/cm2. This was attributed to high optical gap energy and transparency of ZnO compared to Fe2O3. The effects of annealing temperature and concentration of Fe2O3 on conversion efficiency of the Fe2O3 based solar cell were also studied.

Nanocrystalline SnO2 thin film was prepared by cathodic electrodeposition–anodic oxidation and its structure was characterized by X-ray diffraction, SEM, UV–visible absorption and nitrogen adsorption–desorption by BET method. The obtained film has a surface area of 137.9 m2/g with grain sized of 24 nm. Thus the prepared SnO2 thin film can be applied as an electrode in dye-sensitized solar cell. The SnO2 electrode was successfully sensitized by Erythrosin dye and photoelectrochemical measurements indicate that the cell present short-circuit photocurrent (Jsc) of 760 μA/cm2, fill factor (FF = 0.4), photovoltage (Voc = 0.21 V) and overall conversion efficiency (η) of 0.06% under direct sun light illumination. The relatively low fill factor and photovoltage are attributed to the reduction of triodiode by conduction band electrons and intrinsic properties of SnO2.

Thin film and sheet PbS quantum dots (QDs) concentrators were synthesized by sol-gel method using three different PbS concentrations (0.14, 0.2, and 0.4 mol%). The structure and morphology of the prepared PbS QDs were characterized by X-ray diffraction (XRD), Scan electron microscopy (SEM), and Transmission electron microscopy (TEM). The photostability of the PbS QDs concentrators under outdoor exposure to sunlight for 8 weeks was studied. The results showed that the PbS QDs sheet with PbS concentration (0.14 mol%) has the highest luminescence intensity. The sheet PbS QDs concentrator was used to couple with PV solar cell and the corresponding photoelectric conversion efficiency was measured under sun light illumination. I-V characteristics of the photovoltaic devices, both open circuit voltage and short circuit current were improved as compared to the device without collector. This indicates that the proposed technique is very useful for improving the efficiency of solar cell.

This work presents an experimental and theoretical study of cyanidin natural dye as a sensitizer for ZnO dye-sensitized solar cells. ZnO nanoparticles were prepared using ammonia and oxalic acid as a capping agent. The calculated average size of the synthesized ZnO with different capping agents was found to be 32.1 nm. Electronic properties of cyanidin and delphinidin dye were studied using density functional theory (DFT) and time-dependent DFT with a B3LYP/6-31G(d,p) level. By comparing the theoretical results with the experimental data, the cyanidin dye can be used as a sensitizer in dye-sensitized solar cells. An efficiency of 0.006% under an AM-1.5 illumination at 100 mW/cm(2) was attained. The influence of dye adsorption time on the solar cell performance is discussed.