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The use of renewable resources including solar energy has become a mandatory approach to reduce the repercussions of the excessive use of fossil fuels. Recently, there has been an exponential increase in the research of solar cells of various types, which led to their storming the international economic market as a safe source of energy. Silicon-based solar cells (Si-based SCs) occupied the throne of solar cells until the advent of perovskite solar cells (PSCs), which captured the attention of scientists around the world with its high and rapid tide in the values of their efficiencies, which exceeds 25% and predicted to reach the Shockley–Queisser limit. This review takes, in summary, a general tour in the world of PSCs to discuss the perovskite emergence and its composition materials, the components of PSCs, the unique properties of hybrid organic–inorganic perovskites (HOIPs) that stand behind the high-performance devices, the PSC architectures and their fabrication processes, the industrial challenges and finally a future view on PSC fate.

Cu and N-doped TiO2 photocatalysts were synthesized from titanium (IV) isopropoxide via a microwave-assisted sol-gel method. The synthesized materials were characterized by X-ray diffraction, UV-vis diffuse reflectance, photoluminescence (PL) spectroscopy, SEM, TEM, FT-IR, Raman spectroscopy, photocurrent measurement technique, and nitrogen adsorption–desorption isotherms. Raman spectra and XRD showed an anatase phase structure. The SEM and TEM images revealed the formation of an almost spheroid mono disperse TiO2 with particle sizes in the range of 9-17 nm. Analysis of N2 isotherm measurements showed that all investigated TiO2 samples have mesoporous structures with high surface areas. The optical absorption edge for the doped TiO2 was significantly shifted to the visible light region. The photocurrent and photocatalytic activity of pure and doped TiO2 were evaluated with the degradation of methyl orange (MO) and methylene blue (MB) solution under both UV and visible light illumination. The doped TiO2 nanoparticles exhibit higher catalytic activity under each of visible light and UV irradiation in contrast to pure TiO2. The photocatalytic activity and photocurrent ability of TiO2 have been enhanced by doping of the titania in the following order: (Cu, N) - codoped TiO2 > N-doped TiO2 > Cu-doped TiO2 > TiO2. COD result for (Cu, N)-codoped TiO2 reveals ∼92% mineralization of the MO dye on six h of visible light irradiation. Keywords: TiO2, Nanoparticles, Doping, COD, Photocatalytic activity

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.

Ag@Ag2O/RGO nanocomposites with different loads of Ag (0.4%–8.5%) were synthesized using a simple deposition method in the presence of a triblock copolymer template at different annealing temperatures (250 °C and 400 °C). All samples were characterized with various techniques such as XRD, FTIR, Raman, TEM-SAED, N2 sorptiometry and UV-Vis diffuse reflectance. The supercapacitor performance of the samples was measured. Besides, the catalytic performances of the samples towards 4-nitrophenol (4-NP) reduction were tested under dark conditions. The results revealed the well dispersion of Ag and Ag2O moieties on RGO with crystallite size in the range of 17–34 nm. The nanocomposite Ag@Ag2O/RGO annealed at 400 °C exhibited the highest reduction rate constant for 4-NP reduction (0.01 s−1). In addition, this composite has shown the highest specific capacitance of 312 F g−1 at scan rate of 20 mV s−1 and 119 F g−1 at a current density of 11 mA g−1.

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.

Silica and montmorillonite-supported silica nanoparticles were prepared via an acid one step sol-gel process. The synthesized solids were characterized using XRD, FTIR, TEM and N2 adsorption. The effect of preparing temperatures on the structure and properties of the silica nanoparticles were studied. The results show that the increase of annealing temperature from 25 to 200℃, don’t change amorphous state of silica. While for montmorillonite-supported silica the clay platelets are delaminated during the sol-gel process. TEM results showed that the average particle size of silica is increased by increasing temperature due to the particle sintering and the clay-silica nanoparticles possessed core–shell morphology with diameter of 29 nm. The surface area measurements showed that by increasing annealing temperature the surface area was decreased due to aggregation of particle. The clay-silica sample showed lower average pore width than that of the silica prepared at 200℃ indicating that it has a macropores structure. The adsorption efficiency of the prepared samples was tested by adsorption of protoporphyrin IX. The highest adsorption efficiency was found for SiO2 prepared at 200℃. Temkin model describe the equilibrium of adsorption of protoporphyrin IX on caly-silica nanoparticles under different conditions.

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.

Polyaniline/silver (PANI/Ag) nanocomposite was prepared by chemical oxidative polymerization of aniline monomer in the presence of nitric acid. The formation of PANI/Ag nanocomposite was characterized by XRD, FTIR, TEM, UV-vis spectroscopy. The XRD patterns indicated that the crystalline phase of Ag is cubic with crystallite size of 93 nm. The TEM image shows that the Ag nanoparticles are well dispersed in the polyaniline matrix. Optical measurements show that the value of optical band gap of nanocomposite is lower than that of pure PANI. The DC-, AC-conductivities, dielectric permittivity (e') and dielectric loss (e'') of (PANI/Ag) nanocomposite and pure PANI have been measured in the temperature range from 303 to 723 K and frequency range from 10 to 103 kHz. The electrical conductivity of the (PANI/Ag) nanocomposite is higher than pure PANI. Temperature variation of frequency exponents in this blend suggests that AC-conductivity is attributed to correlated barrier hopping mechanism. At all frequencies, the e' value for (PANI/Ag) nanocomposite is higher than that for pure one. The higher dielectric constant of the PANI/Ag nanocomposite indicates their better ability to store electric potential energy under the influence of alternative electric field.

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.

We have developed dye-sensitized nanocrystalline CdS and ZnS solar cells (DSSCs) based on crystal violet, methylene blue, and fluorescein photosensitizers. Nanocrystalline CdS and ZnS were synthesized by a green synthesis method using starch as the capping agent. Characterization of nanocrystalline CdS and ZnS was carried out by optical absorption and x-ray diffraction. The results indicate that CdS and ZnS prepared by this method may be used as photoelectodes in photo-electro-chemical energy conversion systems. DSSCs have been built and their photocurrent, open-circuit voltage, fill factor, and efficiency have been measured under direct sunlight illumination (1000 Wcm−2). The efficiency of the cells made from dye-CdS was much higher than that of the cells made from dye-ZnS. This can be attributed to the particle size effect. Among the prepared dye-sensitized solar cells, a DSSC based on fluorescein dye as the photosensitizer produced the highest overall light solar energy to electricity conversion efficiency.

Problem statement: Current researches had shown that the photostability of a luminescent solar collector depend on the method of its preparation and type of using dye. This research therefore aimed at studying the stability of luminescent solar collector prepared by sol-gel spin coating method using Ponceau 2R. Approach: The effect of silica matrix on the photostability and fluorescence properties of Ponceau 2R was investigated in terms of concentration using absorption and emission techniques. The photostability of Ponceau 2R doped sol-gel samples was also examined through 60 days exposure to sunlight. Results: The dye in the solid matrix had absorption and emission characteristics different from those in the liquid solution. The transition energy for electrons were direct allowed transition for all examined concentrations and there is no variation in the values of optical gap Energy (Eg) by increasing the dye content or exposure times. The dependence of the width of the tails of the localized states in the band gap (Eu) on the concentration and exposure times were also studied. The emission spectra for the samples before and after exposure to sunlight showed that the sample of concentration 0.1 wt% had the highest fluorescent intensity and fluorescence quantum yield. Conclusion/Recommendations: This study showed that Ponceau 2R of 0.1 wt% concentration has a good potential for application in a luminescent solar collector using sol-gel techniques.

CdS quantum dot (QD) solar concentrators were prepared by a sol–gel spin coating method. Thin films were prepared at different annealing temperatures and characterized by X-ray diffraction and spectroscopic techniques. The effect of temperature on the optical properties of CdS QDs embedded in silica matrix was assessed before and after exposure of the samples to sunlight for up to 4 weeks. The results show that as the annealing temperature increases, the fluorescent intensity and Stokes shift decrease. Therefore lower temperatures are preferable for the preparation of highly efficient QD solar concentrator systems.

Oxidative stress is a basic mechanism behind the development of diabetic retinopathy (DR). Therefore, the present study conducted to evaluate the protective effect of zinc oxide nanoparticles (ZnONPs) doped with fluorine (F:ZnO) and chlorine (Cl:ZnO), on retinal oxidative stress in type II diabetic rats. TEM showed that the F:ZnO and Cl:ZnO have average particle size 17.7 and 59.3 nm, respectively. The results indicated that serum glucose was increased significantly (p ≤ 0.05) and serum insulin was decreased significantly 3 days after treatment with STZ compared to other groups. STZ treatment depleted both retinal and liver TBA and retinal GST contents. While, simultaneous treatment rats with low and high dose of STZ + F:ZnO and STZ + Cl:ZnO were decreased serum glucose induced by STZ and reversed the deplete influence on GSH level of retinal and reduced the highs in TBA levels of livers and retinas in STZ -administrated rats. The results investigate the useful effects of high dose of F:ZnO and Cl:ZnO in protection diabetic rats against hyperglycemia and retina against oxidative stress.

Luminescent solar concentrator samples using polymethylmethacrylate (PMMA) as the matrix with phthalocyanine, nickel-phthalocyanine and hematoporphyrin IX dichloride laser dyes were prepared by a casting method. Optical absorption measurements were carried out at room temperature across the 200–900 nm wavelength region both before and after the samples were exposed to sunlight for two weeks. The degradation of PMMA–dye samples, measured by absorption, was found to obey a first-order kinetic equation. Values of the optical band gaps ( E g ) have been obtained for the direct allowed transitions before and after the samples were exposed to sunlight. The tail width of localized states in the band gap ( E u ) was calculated from Urbach’s formula. Photodegradation studies revealed that the phthalocyanine dye systems are the most stable. Emission spectra and quantum efficiency were also investigated, and phthalocyanine dyes were shown to have a lower Stokes shift and a higher fluorescence quantum yield ( Q f ) than the hematoporphyrin IX dichloride. Collectively, these results suggest that PMMA doped with phthalocyanines provide the better system for use in fluorescent solar collector systems.

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 note corrects an error in the math of [Appl. Opt.55, 838 (2016)APOPAI0003-693510.1364/AO.55.000838] and reports a deletion of text that should have occurred in production.

The electrical properties: DC-electrical conductivity (σDC), AC-electrical conductivity (σAC), dielectric permittivity (ɛ′) and dielectric loss (ɛ″) for pure polymethylmethacrylate (PMMA) and mixed with phthalocyanine, Ni-phthalocyanine and hematoporphyrin IX chloride laser dyes have been investigated. The conductivity values for all polymer–dye samples are higher than that of the pure PMMA. For all investigated samples, at the constant temperature, the frequency dependence of (σAC) was found to obey the relation (σAC) = Aωs. The results are discussed according to the correlated barrier hopping CBH mechanism from which the Coulomb well barrier of charge carriers (WM) was calculated. For the dye-doped samples, the hematoporphyrin IX chloride mixed sample showed the larger value of (WM) compared with the others. At all frequencies, ɛ′ values for doped samples are higher than that of pure one. This is due to a free volume enhancement offered by the large size of the dye molecule. Also, the addition of dyes to PMMA causes an increase in the intensity of the loss peak (ɛ″) accompanied by a shift in its position. The effect of chemical structure of investigated dyes on the electrical properties is discussed.