Sharif Digital Repository

Luminescence downshifting (LDS) of light can be a practical photon management technique to compensate the narrow absorption band of high-extinction-coefficient dyes in dye-sensitized solar cells (DSSCs). Herein, an optical analysis on the loss mechanisms in a reflective LDS (R-LDS)/DSSC configuration is reported. For squaraine dye (550-700 nm absorption band) and CaAlSiN3:Eu2+ LDS material (550-700 nm emission band), the major loss channels are found to be non-unity luminescence quantum efficiency (QE) and electrolyte absorption. By using an ideal LDS layer (QE=100 %), a less absorbing electrolyte (Co-based), and antireflection coatings, approximately 20% better light harvesting is obtained.... 

A TiO2replica of ZnO nanosheet films is synthesized using a chemical replacement process. ZnO nanosheets are grown by electrodeposition on fluorine doped tin oxide (FTO) films, and a dissolution/deposition process is used to convert the ZnO template into a TiO2replica. Electron microscopy shows the final TiO2structure follows the morphology of the initial ZnO template. X-ray diffraction and energy dispersive spectroscopy verify the total transformation of ZnO to TiO2. The as-synthesized TiO2sheets are amorphous and after annealing turn into the anatase phase. The film of TiO2nanosheets is used as the photoanode of a dye sensitized solar cell. Despite the low roughness factor of 100, a... 

Hollow silver microspheres are synthesized in an easy and environmentally friendly process by a sacrificial templating method. Carbonaceous microspheres (CMSs) are used as hard templates, which have been synthesized previously by a hydrothermal carbonization process. Hollow silver spheres (HSSs) are synthesized by thermal removal of the core carbon component. The thickness of shell could be controlled by the concentration of precursors. Depending on the thickness, uniform or discontinuous shells are formed. The spheres are coated with SiO 2, and then added into the electrolyte of a dye solar cell. The enhancement of 50% is achieved in short-circuit current density (JSC) due to the scattering... 

We propose and theoretically evaluate a plasmonic light trapping solution for thin film photovoltaic devices that comprises a monolayer or a submonolayer of wavelength-scale silver particles. We systematically study the effect of silver particle size using full-wave electromagnetic simulations. We find that light trapping is significantly enhanced when wavelength-scale silver particles rather than the ones with subwavelength dimensions are used. We demonstrate that a densely packed monolayer of spherical 700 nm silver particles enhances integrated optical absorption under standard air mass 1.5 global (AM1.5G) in a 7 μm-thick N719-sensitized solar cell by 40% whereas enhancement is smaller... 

In this study a novel symmetrical metal-free organic dye for applications in dye-sensitized solar cells (DSSCs) was synthesized. This dye (D) was designed with A-π-D-π-A framework and synthesized with 9,9-dioctylfluorene as electron donor, phenylene as π-spacer and cyanoacetic acid as electron acceptor. The chemical structure of product was determined using UV-Vis, FT-IR, CNMR, HNMR spectroscopy techniques. The presence of a phenylene π-bridge between the donor and the acceptor units and the di-anchoring moieties in this structure led to enhancement of conjugation lengths and molar extinction coefficient (ε) that is promising for further improvement of the conversion efficiency of DSSCs.... 

In this study a novel symmetrical metal-free organic dye for applications in dye-sensitized solar cells (DSSCs) was synthesized. This dye (D) was designed with A-π-D-π-A framework and synthesized with 9,9-dioctylfluorene as electron donor, phenylene as π-spacer and cyanoacetic acid as electron acceptor. The chemical structure of product was determined using UV-Vis, FT-IR, CNMR, HNMR spectroscopy techniques. The presence of a phenylene π-bridge between the donor and the acceptor units and the di-anchoring moieties in this structure led to enhancement of conjugation lengths and molar extinction coefficient (ε) that is promising for further improvement of the conversion efficiency of DSSCs  

This paper describes the photoluminescence study of titanium dioxide (TiO2) nanorods grown by a hydrothermal synthesis method on the surface of fluorine doped tin oxide (FTO) coated glass. The effects of growth conditions including: reaction time, precursor concentration and adding NaCl to hydrothermal solution on the structural and optical properties of productions are examined by using SEM, XRD, TEM and room temperature photoluminescence measurements. Also, the performance of the TiO2 nanorods as a photoanode of dye sensitized solar cells is investigated. The different excitation energies and intensities are chosen to verify the discrete electronic state of radiative recombination centers... 

We introduce a new third generation of solar cell structure which inserts different-sized quantum dots in the active region of a pin structure. Generating an intermediate band in the bandgap of the host material makes a good overlap with a part of solar spectrum. The effect of the recombination mechanisms on efficiency and currentvoltage characteristics of this intermediate band solar cell is calculated. We deduce that the increase in recombination lifetime of the excited carriers can improve the characteristics of this structure. This result can be a route which helps us to take the effect on solar cell characteristics into consideration  

The alarming energy and environmental crisis of our modern era necessitates scientists to propose alternatives to replace the scarce and harmful fossil fuels. The Sun, as a free, and abundant clean energy resource, presents a motivation for researchers to convert the sunlight to electrical power and store the H2 as an energy carrier by developing solar cells as well as water splitting devices, respectively. One of the fundamental parts of a solar energy convertor (solar cell/photoelectrochemical device), where the reduction reaction occurs, is the counter electrode (CE); the CE is commonly based on rare Pt. It is critical to substitute costly CEs with efficient, low-cost replacements, which... 

We propose a nano-plasmonic thin-film solar cell (TFSC) as a receiver for the visible light communication (VLC). The presented design is a novel and optimized structure that can be used instead of photodetectors and power supplies in the VLC. The plasmonic TFSC that described in this work is capable of increasing the light absorption in comparison with the conventional thick Si solar cell without plasmonic nanostructures. However, plasmonic nanoparticles can improve the absorption of Si solar cell in a visible range of solar spectra. In this paper, different situations for inserting nanoparticles in an active layer are considered and the absorption is calculated as a function of particle... 

There have been recent reports on the formation of single-halide perovskites, CH3NH3PbX3 (X=Cl, Br, I), by means of vapor-assisted solution processing. Herein, the successful formation of mixed-halide perovskites (CH3NH3PbI3−xXx) by means of a vapor-assisted solution method at ambient atmosphere is reported. The perovskite films are synthesized by exposing PbI2 film to CH3NH3X (X=I, Br, or Cl) vapor. The prepared perovskite films have uniform surfaces with good coverage, as confirmed by SEM images. The inclusion of chlorine and bromine into the structure leads to a lower temperature and shorter reaction time for optimum perovskite film formation. In the case of CH3NH3PbI3−xClx, the optimum... 

A luminescent coating of CaAlSiN3:Eu2+ particles applied on photoanode (TiO2) layer of SQ1 sensitized solar cell by doctor blading the paste of phosphor particles. The luminescent layer acted as a dual functional layer and enhanced the short circuit current density (JSC) by 64% via both scattering effect and downshifting of the photons in 400-600nm spectral range to photons in 600-800nm spectral range. Considerable relative enhancement in incident photon to current conversion efficiency (IPCE) up to 350% in 400-600nm spectral range proves the down shifting effect as the dominant factor for the improved performance of dye sensitized solar cell (DSSC). © 2016 Elsevier B.V  

Fabrication of organohalide perovskite materials on the top of ZnO nanoparticles (NPs) has some beneficial advantages such as room temperature processing; however, the perovskite is not stable on ZnO NPs layer during the annealing process. In fact, there are only a few reports about the fabrication of perovskite solar cells on ZnO NPs layer. Herein, the decomposition mechanism of CH3NH3PbI3 perovskite materials on ZnO is reported, and it is found that the perovskite film on the top of the ZnO layer is converted into PbI2 during the annealing process due to the existence of hydroxide groups on the surface of the ZnO NPs. Depending on the annealing temperature, the reaction rate and the... 

A series of bithiazole-based dye sensitizers have been designed by employing various electron-rich moieties as π-spacer, which are based on the reported experimentally synthesized dye T-BT, to shed a light on the impact of both the nature and position of electron-rich moiety on the efficiency of dyes in DSSCs. To evaluate the efficiency of these dyes, various key parameters associated with overall conversion efficiency (η), including electronic and optical properties of free dyes are calculated, based on the computational methods. Besides, the dye/TiO2 structures have been taken into account to investigate the interfacial features of the dye sensitizers adsorbed on TiO2 semiconductor and... 

Relative to the broadband solar spectrum, a narrow range of spectral absorption of photovoltaic (PV) devices is considered an important determinant that the efficiency of light harvesting of these devices is less than unity. Having the narrowest spectral response to solar radiation among all PV devices, dye-sensitized solar cells (DSSCs) suffer severely from this loss. Luminescent spectral conversion provides a mechanism to manipulate and to adapt the incident solar spectrum by converting, through photoluminescence, the energies of solar photons into those that are more effectively captured by a PV device. This mechanism is particularly helpful for DSSCs because there is much flexibility in... 

In this work the influence of different particulate gels on morphology and photoelectric performance of TiO2 dye-sensitized solar cells (DSCs) is studied. Two coagulant and flocculant agents are used to convert a TiO2 particulate sol into the gels using double layer compression and charge neutralization mechanisms. One more TiO2 particulate gel is also prepared by changing the pH of the sol using acid: alkoxide molar ratio higher than the critical ratio to obtain an unstable sol. Based on X-ray diffraction (XRD) analysis, the films contain primary nanoparticles with average crystallite size of 13–15 nm. Field emission scanning electron microscopy (FE-SEM) images show uniform, nanostructured... 

A luminescent coating of CaAlSiN3:Eu2+ particles applied on photoanode (TiO2) layer of SQ1 sensitized solar cell by doctor blading the paste of phosphor particles. The luminescent layer acted as a dual functional layer and enhanced the short circuit current density (JSC) by 64% via both scattering effect and downshifting of the photons in 400–600 nm spectral range to photons in 600–800 nm spectral range. Considerable relative enhancement in incident photon to current conversion efficiency (IPCE) up to 350% in 400–600 nm spectral range proves the down shifting effect as the dominant factor for the improved performance of dye sensitized solar cell (DSSC). © 2016 Elsevier B.V  

A new poly (acrylonitrile) (PAN)-based gel polymer electrolyte (GPE) is fabricated to study the effect of carbon nanotube (CNT) on dye-sensitized solar cell (DSSC) efficiency. The GPEs are examined using electrochemical impedance spectroscopy (EIS) to analyze ionic conductivity. A maximum of 4.45 mS cm−1 ionic conductivity is achieved at room temperature with incorporation of 11 wt.% CNT. Performance of DSSC is examined with a solar simulator, and the highest energy conversion efficiency of 8.87% is achieved with the addition of 11 wt.% CNT. All GPE samples are found to follow Arrhenius model with temperature-dependent ionic conductivity testing. Structural properties are also characterized... 

A new poly (acrylonitrile) (PAN)-based gel polymer electrolyte (GPE) is fabricated to study the effect of carbon nanotube (CNT) on dye-sensitized solar cell (DSSC) efficiency. The GPEs are examined using electrochemical impedance spectroscopy (EIS) to analyze ionic conductivity. A maximum of 4.45 mS cm −1 ionic conductivity is achieved at room temperature with incorporation of 11 wt.% CNT. Performance of DSSC is examined with a solar simulator, and the highest energy conversion efficiency of 8.87% is achieved with the addition of 11 wt.% CNT. All GPE samples are found to follow Arrhenius model with temperature-dependent ionic conductivity testing. Structural properties are also characterized... 

Abstract: The present research comes up with optimizing the layers thickness of a Ruddlesden–Popper perovskite with the general formula of (S0.97S0.03 ')2[Cs0.05(FA0.097MA0.03)0.95]n – 1Pbn(I0.97Br0.03)3n + 1 for efficient, stable solar cell applications. Such a triple-cation quasi-two-dimensional (2D) structure simultaneously contains two spacers, namely 5-ammonium valeric acid iodide (S) and tetra-n-octylammonium bromide (S'). Systematic studies showed that morphology, crystal structure, optical properties, photovoltaic performance, and internal resistances of this compound depended upon the value of the n integer. Field emission scanning electron microscopy set forth that the deposited...