Sharif Digital Repository

A new strategy for enhancing the efficiency of TiO2 dye-sensitized solar cells (DSSCs) by design of a new double layer film doped with Cr ions, with various morphologies, is reported. X-ray diffraction and field emission scanning electron microscope (FE-SEM) analyses revealed that the synthesized nanoparticles had uniform and nanometer grains with different phase compositions and average crystallite size in the range of 10-12 nm depending upon Cr atomic percentage. UV-vis absorption showed that Cr introduction enhanced the visible light absorption of TiO2 nanoparticles by shifting the absorption onset to visible light region. Furthermore, the band gap energy of nanoparticles decreased with... 

Aggregated sub-micron size nitrogen doped TiO2 (N-TiO2) particles with superior optical and electrical features were successfully synthesized for embedding into commercial mesoporous TiO2 photoelectrode of dye sensitized solar cells (DSSCs) as the light scattering particles compared to undoped one. X-ray photoelectron spectroscopy and absorption spectra confirmed that the titanium dioxide is sufficiently doped by nitrogen in N-TiO2 sample. Employing these high-surface N-TiO2 in mesoporous photoelectrode of solar cells, the power conversion efficiency of 8% has been achieved which shows 17% improvement for the optimum embedded level of... 

We present a new dandelion-like TiO2 spheres by a modified hydrothermal method for manufacture of dye-sensitized solar cells (DSSCs). This construct is composed of numerous nanowires for employment as the scattering layer of DSSCs. Such morphology is produced by nucleation-growth-assembly mechanism. The size of the dandelion-like spheres and their morphology can be tailored by controlling the processing parameters of the modified hydrothermal process. TiO2 nanoparticles with narrow size distribution are also synthesized by hydrothermal route for the active layer of DSSCs. The nanoparticles show pure anatase phase with average size of 40 nm, whereas the dandelion-like TiO2 spheres are pure... 

This paper gives the design and analysis approaches for the class-E power amplifier with a shunt inductor under the nominal conditions, i.e., zero-current switching (ZCS) and zero-current derivative switching (ZCDS), with taking into account the MOSFET nonlinear output parasitic capacitance at any duty ratio. Although, the class-E ZCS/ZCDS conditions obtained high-efficiency, but the switch-current waveform affected by the slope of the voltage across the MOSFET nonlinear drain-to-source parasitic capacitance during the switch-off state, which restricted the operating frequency. On the other hand, the duty ratio is an adjustment parameter to obtain high-frequency operation. Therefore, the... 

The plasmonic effects of infiltrated silver (Ag) nanoparticles, with different contents, inside a nanostructured TiO2 film on the photovoltaic performance of dye-sensitized solar cells (DSSCs) are explored. The synthesized Ag nanoparticles are immobilized onto deposited TiO2 nanoparticles by a new strategy using 3-mercaptopropionic acid (MPA), a bifunctional linker molecule. Transmission electron microscope (TEM) images show that monodispersed Ag and polydispersed TiO2 nanoparticles have an average diameter of 12 ± 3 nm and 5 ± 1 nm, respectively. Moreover, Fourier transform infrared spectroscopy (FTIR) analysis reveals that Ag nanoparticles were successfully functionalized and capped with... 

Herein, we demonstrate a facile low temperature chemical bath deposition approach to deposit a light scattering layer on a nanostructured mesoporous TiO2 bottom layer in a dye-sensitized solar cell architecture. Large TiO2 nanoparticles were formed on the top surface of photoanode electrodes via hydrolysis of TiCl4 at 70 °C. We controlled the size and agglomeration of these TiO2 nanoparticles by altering the concentration of TiCl4 in the chemical bath during the hydrolysis process. Electron microscope images revealed that mono-dispersed scattering particles having uneven surfaces with diameters between 100 to 300 nm formed on the mesoporous titania layer. The scattering behavior of the... 

Copper sulfide deposited ZnO nanorods (ZnO NRs/CuS) have been applied as a new counter electrode material with high electrocatalytic activity towards polysulfide electrolyte, which results in the formation of a highly efficient counter electrode for QDSSCs. It was observed from the current density-voltage (J-V) characteristics that the short-circuit current density (Jsc), power conversion efficiency (PCE), and fill factor (FF) were enhanced from 7.63 mA cm-2 to 14.48 mA cm-2, 1.59% to 4.18%, and 0.29 to 0.38, respectively, when a bare CuS counter electrode was changed to a ZnO NRs/CuS counter electrode. Electrochemical impedance spectroscopy (EIS), Tafel polarization and cyclic voltammetry... 

We report a new facile strategy to enhance the efficiency of TiO2 dye-sensitized solar cells (DSSCs) using Nb-doped TiO2 photoelectrodes with carbon nanotube-derived TiO2 nanotubes (CDTs). Multi-walled carbon nanotubes (CNTs) with an average diameter of 80 nm are used as the template to produce CDTs through facile sol-gel and oxidation processes at 600 °C. Field emission scanning electron microscope (FESEM) and X-ray diffraction (XRD) analyses reveal that the synthesized CDTs have a uniform thickness of 60-120 nm and a crystallite size of 17 nm. We prepare Nb-doped TiO2 nanoparticles with different atomic ratios of 0-4 at% Nb and test them as photo-electrodes to investigate the doping... 

Dielectric scattering particles have widely been used as embedded scattering elements in dye-sensitized solar cells (DSCs) to improve the optical absorption of the device. Here we systematically study rodlike and spherical core-shell silica@Ag particles as more effective alternatives to the dielectric scattering particles. The wavelength-scale silica@Ag particles with sufficiently thin Ag shell support hybrid plasmonic-photonic resonance modes that have low parasitic absorption losses and a broadband optical response. Both of these features lead to their successful deployment in light trapping in high-efficiency DSCs. Optimized rodlike silica@Ag@silica particles improve the power conversion... 

Herein we report for the first time on efficient and environmentally friendly bioenergy production from bacteriorhodopsin (bR) and green florescent protein (GFP) as co-sensitizers. bR as a transmembrane protein, acts like a light-driven proton pump in Halobacterium salinarum, converting light energy into a proton gradient. Employing GFP beside bR can enhance the photo-bioenergy production efficiency in two aspects: GFP can increase short circuit current by improvement in light absorption either by extending the sensitizingspectrumor making fluorescence in absorption region of bR. It can also enhance open circuit voltage more than 150 mV by improvement in photoelectrode converging and... 

The compatibility of atomic layer deposition directly onto the mixed halide perovskite formamidinium lead iodide:methylammonium lead bromide (CH(NH2)2, CH3NH3)Pb(I,Br)3 (FAPbI3:MAPbBr3) perovskite films is investigated by exposing the perovskite films to the full or partial atomic layer deposition processes for the electron selective layer candidates ZnO and SnOx. Exposing the samples to the heat, the vacuum, and even the counter reactant of H2O of the atomic layer deposition processes does not appear to alter the perovskite films in terms of crystallinity, but the choice of metal precursor is found to be critical. The Zn precursor Zn(C2H5)2 either by itself or in combination with H2O during... 

We decorated Zn-doped TiO2-nanoparticle-based photoanodes with carbon nanotube (CNT)-derived TiO2 nanotubes (TNs) to enhance the power conversion efficiency of dye-sensitized solar cells (DSCs). X-ray photoelectron spectroscopy analysis verified that Zn ions, in the range of 0 to 1 at %, were successfully doped into the TiO2 lattice. Field-emission SEM and TEM images of the TNs, as derived from the sol–gel template-assisted route, revealed that a uniform TiO2 coating with a thickness of 60 to 120 nm was deposited on the surface of the CNT template through a noncovalent route. We observed that the cell efficiency improved from 6.80 for pure TiO2 to 7.52 for 0.75 at % Zn-doped TiO2... 

Solar cells with high efficiency, low cost, and high stability are the target for the new generation of solar cells. A fully printable perovskite (CH3NH3PbI3) solar cell (PSC) with device architecture FTO/TiO2/Al2O3/NiOx/C is fabricated in the current research as a low-cost and relatively stable structure and is investigated to determine how different fabrication factors such as the thickness of the insulating spacer layer (Al2O3) or treatments such as heat and UV-O3 treatments can affect the interfacial properties of this multilayer mesoporous structure. X-ray photoelectron spectra (XPS) show that UV-O3 treatment increases the Ni3+(Ni2O3) phase on the surface of the black nickel oxide layer... 

This paper presents solid-state ligand exchange of spin-coated colloidal lead sulfide quantum dot (PbS QD) films by methylammonium iodide (MAI) and integration of them in depleted heterojunction solar (DHS) devices having an antireflecting (AR) nanocone plastic structure. Time-resolved photoluminescence measurements determine a shorter lifetime of the charge carries on a semiconductor (TiO2) electron transfer layer for the MAI-passivated QD films as compared with those with long-chain aliphatic or short thiol ligands. Consequently, the DHS device yields improved power conversion efficiency (>125%) relative to oleic-acid-passivated PbS QD films. Using anodized aluminum oxide templates, an... 

Different compositions of TiO2–BaTiO3 nanocomposites are synthesized with various weight ratios for dye-sensitized solar cell (DSSC) applications. TiO2 and BaTiO3 nanoparticles (NPs) are synthesized by sol-gel and solvothermal methods, respectively and are employed as the photoanode electrodes. BaTiO3 NPs have pure cubic perovskite crystal structure with an average size of 20-40 nm, while TiO2 NPs show pure anatase phase with 15-30 nm size. The power conversion efficiency (PCE) enhancement of the cells is first attained by controlling the thickness of the films for light harvesting improvement. The fabricated DSSC composed of pure BaTiO3 NPs with an optimal thickness of 25 μm shows... 

We develop a facile route for deposition of mesoporous TiO2 thick films over several micrometers by sol–gel and evaporation-induced self-assembly processes using Pluronic F127. The light harvesting of deposited films by two different methods (i.e., using a viscous gel and a paste) is studied by controlling their mesoscopic characteristics, phase composition and thickness for dye-sensitized solar cells applications. It is revealed that the mesoscopic films have mixtures of anatase and rutile crystal structures with surface area in the range 50.6–94.6 m2/g. We observe that the mesoporous TiO2 films prepared under optimized conditions improve light harvesting and dye loading of photoelectrodes.... 

Today manufacturing of high efficiency chalcogenide thin film solar cells is based on high cost vacuum-based deposition processes at high temperature (>500 °C) and in chalcogen -containing atmosphere. In this paper, we introduce a simple vacuum-free and selenization-free, solution processing for fabricating a superstrate-type CuInS2 (CIS) solar cell. The absorber, buffer and blocking layers were all deposited by spin coating of molecular precursor inks. We demonstrate the deposition of In2S3 buffer layer by sol-gel spin casting for the first time. The rapid sintering process of CIS layer was carried out at 250 °C that is considered a very low temperature in CIGS thin-film technologies. A... 

Thin-film solar cells based on hybrid organo-halide lead perovskites achieve over 22% power conversion efficiency (PCE). A photovoltaic technology at such high performance is no longer limited by efficiency. Instead, lifetime and reliability become the decisive criteria for commercialization. This requires a standardized and scalable architecture which does fulfill all requirements for larger area solution processing. One of the most highly demanded technologies is a low temperature and printable conductive ink to substitute evaporated metal electrodes for the top contact. Importantly, that electrode technology must have higher environmental stability than, for instance, an evaporated silver... 

In the past few years, organic–inorganic metal halide ABX3 perovskites (A = Rb, Cs, methylammonium, formamidinium (FA); B = Pb, Sn; X = Cl, Br, I) have rapidly emerged as promising materials for photovoltaic applications. Tuning the film morphology by various deposition techniques and additives is crucial to achieve solar cells with high performance and long-term stability. In this work, carbon nanoparticles (CNPs) containing functional groups are added to the perovskite precursor solution for fabrication of fluorine-doped tin oxide/TiO2/perovskite/spiro-OMeTAD/gold devices. With the addition of CNPs, the perovskite films are thermally more stable, contain larger grains, and become more... 

The effect of substitutional Li doping into NiOx hole transporting layer (HTL) for use in inverted perovskite solar cells was systematically studied. Li doped NiOx thin films with preferential crystal growth along the (111) plane were deposited using a simple solution-based process. Mott-Schottky analysis showed that hole carrier concentration (NA) is doubled by Li doping. Utilizing 4 % Li in NiOx improved the power conversion efficiency (PCE) of solar devices from 9.0 % to 12.6 %. Photoluminescence quenching investigations demonstrate better hole capturing properties of Li:NiOx compared to that of NiOx, leading to higher current densities by Li doping. The electrical conductivity of NiOx is...