Sharif Digital Repository

Well-crystallized TiO2 and neodymium (Nd)-doped TiO2 nanoparticles with various doping levels were synthesized by hydrothermal method and utilized as the photoanode of nanostructured solar cells. The results indicated that Nd-doping was caused the absorption spectra shift to higher wavelength while the morphology and surface area were unchanged. As a result, by employing 0.4 mol% Nd in the TiO2 photoelectrode, the overall conversion efficiency of the cell reached 9.08% which is 26% higher than pure one. Based on the photo-electrochemical characterizations, the improvement is a consequence of electrons injection increment from dye to TiO2 conduction... 

As one of the cleanest energies, hydrogen has attracted much attention over the past decade. Hydrogen can be produced using water electrolysis in a Proton Exchange Membrane Electrolysis Cell (PEMEC). In the present study, the performance of the PEMEC, powered by the Photovoltaic-Thermal (PVT) system, is scrutinized. It is considered that the PVT system provides the required electrical power of the PEMEC and preheats the feedwater. A comprehensive numerical model of the coupled PVT-PEMEC system is developed. The model is used to investigate the effect of various operating parameters, including solar radiation intensity, inlet feedwater temperature, and feedwater mass flow rate, on the... 

As one of the cleanest energies, hydrogen has attracted much attention over the past decade. Hydrogen can be produced using water electrolysis in a Proton Exchange Membrane Electrolysis Cell (PEMEC). In the present study, the performance of the PEMEC, powered by the Photovoltaic-Thermal (PVT) system, is scrutinized. It is considered that the PVT system provides the required electrical power of the PEMEC and preheats the feedwater. A comprehensive numerical model of the coupled PVT-PEMEC system is developed. The model is used to investigate the effect of various operating parameters, including solar radiation intensity, inlet feedwater temperature, and feedwater mass flow rate, on the... 

In this work, the combination of H2O2 and an active visible-light-driven photocatalyst (Ag-S/PEG/TiO2) was utilized under natural solar radiation for the degradation of 2-nitrophenol (2-NP), and interaction effects between the photocatalyst and hydrogen peroxide were analyzed. For this purpose, experiments were designed using the response surface methodology based on the central composite design. The resulting data was utilized to obtain a model for the prediction of response (the degradation efficiency) as a function of two independent factors (H2O2 concentration and the photocatalyst loading). The statistical analysis indicated that optimum values of each of the two independent factors... 

N-annulated perylene based materials show outstanding and tunable optical and physical properties, making them suitable to be charge transport materials for optoelectronic applications. However, this type of materials has so far not been well studied in solar cells. Here, we develop a new hole transport material (HTM), namely S5, based on perylene building block terms, for organic-inorganic hybrid perovskite solar cells (PSCs). We have systematically studied the influences of the film thickness of S5 on their photovoltaic performance, and a low concentration of S5 with a thinner HTM film is favorable for obtaining higher solar cell efficiency. S5 shows excellent energy alignment with... 

All current highest efficiency perovskite solar cells (PSCs) use highly toxic, halogenated solvents, such as chlorobenzene (CB) or toluene (TLN), in an antisolvent step or as solvent for the hole transporter material (HTM). A more environmentally friendly antisolvent is highly desirable for decreasing chronic health risk. Here, the efficacy of anisole (ANS), as a greener antisolvent for highest efficiency PSCs, is investigated. The fabrication inside and outside of the glovebox showing high power conversion efficiencies of 19.9% and 15.5%, respectively. Importantly, a fully nonhalogenated solvent system is demonstrated where ANS is used as both the antisolvent and the solvent for the HTM.... 

Graphitic carbon nitride (g-C3N4) is a metal-free conjugated polymer constructed from two-dimensional sheets with a bandgap energy of 2.7 eV, which makes it an applicable and efficient visible-active photocatalyst for H2 production. In the present study, the basic concepts and principles of photocatalytic water splitting have been discussed, and a guide for the selection of appropriate photocatalysts, focusing on the g-C3N4 nanomaterials, has been proposed. Our approach is mainly concentrated on evaluating two factors, namely the solar-to-hydrogen (STH) conversion and apparent quantum yield (AQY) for different photocatalysts, to provide an in-depth analysis and a framework for solar H2... 

Recently, graphitic carbon nitride (g-C3N4) has attracted great interest for photo(electro)chemical applications such as sensing, solar energy exploitation, photocatalysis, and hydrogen generation. This paper presents the potential application and benefits of g-C3N4 nanolayers as a green and highly efficient electrode modifier for the detection of trace lead ions in drinking water and urban dust samples. Carbon nitride nanosheets with a thickness of ∼6 A° and lateral of 100–150 nm were prepared through high-temperature polymerization of melamine followed by sonication-assisted liquid exfoliation. A glassy carbon electrode (GCE) was modified by a thin layer of g-C3N4 through drop casting and... 

This paper addresses a low complexity and high efficient cooling system applicable on photovoltaic (PV) system leading to enhance electrical efficiency and provide preheated water. The developed system consists of a photovoltaic panel, a cooling water system establishing a uniform surface temperature, and a solar water heater. According to the proposed system characteristics, the setup is constructed based on a single mono-crystalline solar panel to absorb more solar radiation intensity and generate more electrical energy per area in compare to a poly-crystalline panel. The preheated water produced by absorbed heat from the photovoltaic is conducted to a solar water heater to satisfy... 

This paper addresses a low complexity and high efficient cooling system applicable on photovoltaic (PV) system leading to enhance electrical efficiency and provide preheated water. The developed system consists of a photovoltaic panel, a cooling water system establishing a uniform surface temperature, and a solar water heater. According to the proposed system characteristics, the setup is constructed based on a single mono-crystalline solar panel to absorb more solar radiation intensity and generate more electrical energy per area in compare to a poly-crystalline panel. The preheated water produced by absorbed heat from the photovoltaic is conducted to a solar water heater to satisfy... 

Perovskite solar cells have been appearing as a superior photovoltaic device owing to their high photovoltaic performance and low cost of fabrication. The formation of a compact and uniform perovskite layer with large crystal size is a significant factor to get the best device performance. In this work, polyvinylidene difluoride (PVDF) was used as a ferroelectric polymer additive to fabricate high-performance mesoporous CH3NH3PbI3-xClx mixed-halide perovskite solar cells in a sequential deposition method. Power conversion efficiency has been enhanced from 10.4 to 16.51% in an ambient atmosphere in the presence of an optimized amount of PVDF assuring continuous and smooth layers with large... 

Organic-inorganic perovskite solar cells (PSCs) have gained considerable attention owing to their impressive photovoltaic properties and simple device manufacturing. In general, PSC employs a perovskite absorber material sandwiched between an electron and hole selective transport layer optimized with respect to optimal band alignment, efficient charge collection, and low interfacial recombination. The interfaces between the perovskite absorber and respective selective contacts play a crucial role in determining photovoltaic performance and stability of PSCs. However, a fundamental understanding is lacking, and there is poor understanding in controlling the physical processes at the... 

Herein, we report a double-layer photoanode electrode composed of TiO2 nanoparticles active layer and a mixture of nanoparticles and newly proposed skein-like nanotubes (NTs) top layer. Such structure performs well in solar light harvesting due to first, the top layer exhibits superior light scattering and second, the active layer with high dye-loading can make better use of the back-scattered light. The results reveal that 30-40 nm nanoparticles have anatase structure, whereas 5-7 μm skein-like NTs show a mixture of anatase and rutile phases. Photovoltaic measurements demonstrate that by tuning mass ratio between nanoparticles and skein-like NTs, the cells based on single-layer photoanode... 

Different structures of TiO2 photoelectrodes are fabricated with various arrangement modes of the layers. TiO2 nanoparticles, synthesized by stabilizing agent free non-hydrolytic sol–gel method, are employed as the under layer, whereas carbon-doped TiO2 hollow spheres, prepared by hydrothermally grown carbon template, are used as the scattering layer of solar cells. The nanoparticles (22 nm) have anatase structure, while 300–700 nm hollow spheres show mixtures of anatase and rutile phases. X-ray photoelectron spectroscopy confirms that carbon is doped into TiO2 hollow spheres, resulting in a decrease in band gap energy in the range 2.96–3.13 eV compared with 3.04 eV band gap energy for the... 

The morphology of the perovskite layer, the effective extraction of the charge carriers, and their transport are the main factors determining the power conversion efficiency (PCE) of the perovskite solar cells (PSCs). In this work, we demonstrated that the geometric and electronic structures of the PSCs could be modified by using a conductive polymer additive in the lead (Pb) halide layer prepared by a two-step deposition method. Polypyrrole (PPy) as a conductive polymer is used in the perovskite layers which could increase the PCE of CH3NH3PbI3-xClx mixed-halide PSCs. By adding an optimized amount of PPy, PCE has been raised from 10.4 to 13.2%. PPy acts as a conductive channel facilitating... 

This paper reports on the synthesis of ZnO nanowires (NWs), as well asthe compound nanostructures of nanoparticles (NPs) and nanowires (NWs+NPs) with different coating layers of NPs on the top of NWs and their integration in dye-sensitized solar cells (DSSCs). In compound nanostructures, NWs offer direct electrical pathways for fast electron transfer, and the NPs of ZnOdispread and fill the interstices between the NWs of ZnO, offering a huge surface area for enough dye anchoring and promoting light harvesting. A significant photocurrent density of 2.64mA/cm2 and energy conversion efficiency of 1.43% was obtained with NWs-based DSSCs. The total solar-to-electric energy conversion efficiency... 

A comparative study has been made of hybrid solar cells based on poly(3-hexylthiophene) (P3HT) and different nano-structures of TiO2. Electrospinning, which is a low cost production method for large area nanofibrous films, was employed to fabricate TiO2 nanofibers and spin coating method was employed to fabricate organic-inorganic hybrid solar cells based on P3HT and TiO2 nanostructures. The performance of the hybrid solar cells was analyzed for four density levels of the TiO2 nanostructure. It was found that higher densities of TiO2 leads to more interface area and generates excitons, so that the power conversion efficiency increases to... 

Solar systems are the most promising technologies to reduce building energy consumption. In recent years, one of the popular solar technologies is building integrated photovoltaic-thermal collectors, because of profitability and no need for separate architectural space. In this study, a new combination of glazed building integrated photovoltaic thermal solar collectors and an absorption cooling system, as a trigeneration system, to provide thermal and electrical energy demands of a case study residential building, is proposed. Dynamic simulation of the proposed system is performed using the TRNSYS-MATLAB co-simulator. Because there is no model for the glazed photovoltaic thermal solar... 

In this paper the creation of multiple energy hubs that make up a complex energy network are modeled and optimized for a selection of six scenarios to examine both their financial viability and potential reduction of greenhouse gas emissions. As a proposed case study scenario for the model, three energy hubs are considered: a 'residential complex (RC)', a 'commercial shopping plaza (CS)', and a 'school (S)'. The use of combined heat and power systems, solar photovoltaic, solar collectors and network interaction are also examined for their impact on efficiency and cost. The modeling is undertaken and carried out by General Algebraic Modeling System (GAMS). It is shown that cost can be reduced... 

Different structures of TiO2 photoelectrodes were fabricated with various arrangement modes of the layers. TiO2 nanoparticles were synthesized by a combination of sol–gel and solvothermal methods and were employed as the active layer of solar cells. Hierarchical TiO2 spheres (HTS) and spherical TiO2 particles (STP) were also prepared by hydrothermal and sol–gel processes, respectively, and used as the scattering layer of solar cells. Field emission scanning electron microscope and X-ray diffraction analyses revealed that all synthesized morphologies showed anatase structure with particle size around 20, 200–400 nm and 1.5–2.0 µm for the...