Sharif Digital Repository

This study attempts to investigate a new way for cooling PV cell using natural vapor as coolant. The performance of solar cell was examined on simulated sunlight. The natural vapor encountered backside of PV cell vertically in various distribution and different mass flow rates. Also, the effect of natural vapor temperature in cooling performance was analyzed. Results indicated that the temperature of PV cell drops significantly with increasing natural vapor mass flow rate. In detail, the PV cell temperature decreased about 7 to 16°C when flow rate reaches 1.6 to 5grmin-1. It causes increasing electrical efficiency about 12.12% to 22.9%. The best performance of PV cell can be achieved at high... 

Abstract: A novel simple synthetic procedure for improving cell efficiency and reducing the production cost of TiO2 dye-sensitized solar cells (DSSCs) by modification and optimization of homemade formulated paste is reported. This is achieved in terms of morphological manipulation of deposited monolayer TiO2 films by controlling three processing parameters of paste formulation. These parameters are tailored to obtain a paste with proper viscosity suitable for spin-coating technique and to achieve uniform, homogeneous, and crack-free films with good connections between TiO2 grains and porous structure. Photovoltaic measurements show that TiO2... 

ZnO nanoparticles (NPs) and submicron aggregates (SMAs) were synthesized via a simple precipitation method by changing the amount of zinc acetate di-hydrate in absolute ethanol and synthesis time. Synthesized NPs and SMAs were characterized by FE-SEM, EDS, XRD, PL, and DRS and were used to fabricate dye-sensitized solar cells (DSSCs). The SMAs synthesized at moderate concentration (0.022 M) and with poly-dispersed distribution of the aggregates showed lower density of deep localized trap states as well as enhanced scattering features in comparison to NP-based electrode. As a result, power conversion efficiency (η) of about 2.56% with improved current density (Jsc) of 8.51 mA/cm2 were... 

Embedded dielectric scatterers comprise an important approach for light trapping in dye-sensitized solar cells (DSCs) due to their simple fabrication process. The challenge in applying these scatterers lies in finding the optimal dimensions and concentration of the scatterers. This requires many experiments and it is often quite difficult to have a starting point for optimizing the concentration. Based on theories of light propagation in random media, we propose a simple model for DSCs with embedded silica spherical particles. Then, by full-wave optical calculations, we determine a narrow range for the concentration of silica particles that leads to the largest optical absorption in the... 

Perovskite solar cells have been constructed under the standard procedure by employing soluble tetratriphenylamine-substituted Zn phthalocyanine as hole transporting material. Solution processed device construction was carried out under ambient conditions of 50–60% ambient humidity. Triphenylamine substitution played the double role of imparting solubility to the core metal phthalocyanine as well as to introduce electron-rich ligands, which could enhance the role of Zn phthalocyanine as hole transporter. Indeed, the obtained material was functional. The present data highlight tetratriphenylamine-substituted Zn phthalocyanine as hole transporting material but also highlight the importance of... 

An efficient electrocatalyst for Pt-free I−/I3 − reduction has been synthesized by high temperature treatment of graphene oxide-cobalt phthalocyanine mixtures. The graphitic material was characterized by various techniques and was found to consist of reduced graphene oxide carrying CoN3 entities, obtained by thermal decomposition of cobalt phthalocyanine. This material had an ionization potential equal to 4.9±0.1 eV and thus it was judged appropriate to act as reduction electrocatalyst for the I−/I3 − redox electrolyte. It was subsequently deposited as thin film on FTO electrodes, which were employed as counter electrodes for dye-sensitized solar cells. Its capacity to reduce I−/I3 − redox... 

We have investigated the influence of perovskite morphology on slow and fast charge transport in the perovskite solar cells. Solar cells with different perovskite cuboid sizes (50-300 nm) have been fabricated using various methylammonium iodide concentrations. Both the low-frequency capacitance and hysteresis are maximum for the cell with the largest perovskite grains (300 nm). The low-frequency capacitance is about three orders of magnitude greater than the intermediate frequency capacitance, indicating the great role of ions on the slow responses and hysteresis. The measurement of open-circuit voltage decay indicates that for the large grains of 300 nm up to 70% of Voc remains across the... 

We report on fabrication of halide perovskite solar cells using a two-step spin-spray coating rout. The applied method is one of the most straight forward procedures for fabricating uniform stoichiometry and crystalline perovskite cells. To fabricate a high quality perovskite layer, various concentrations of methyl-ammonium iodide (CH3NH3I) were sprayed on a spin coated PbI2 layer using a simple airbrush gun. The characterization results indicate that the size of cuboid perovskite morphology depends on the concentration of methylammonium iodide in the spray procedure. The photovoltaic performance of the fabricated solar cells has been measured and a high dependency on the cuboid sizes was... 

Copper phthalocyanine can effectively act as alternative small molecule hole transporting material in perovskite solar cells. In order to produce solution processed devices, a soluble copper phtalocyanine has been synthesized by n-butyl substitution and it was compared to commercially available tert-butyl substituted copper phthalocyanine. It was found that the configuration of the butyl chain plays a very important role in film conductivity and in the subsequent efficiency of solar cells, n-bytyl derivative being the most effective hole transporter. Such a result is due to the fact that n-butyl derivative allows better packing of the molecules in the film and stronger π-π interaction  

Carbazole is an alternant polycyclic aromatic hydrocarbon consisting of three fused rings with a large, aromatic system, containing nitrogen atom showing extensive electron delocalization. In this work, carbazole applied as π-conjugated bridge to construct electron donor–π–electron acceptor (D–π–A) organic dyes, where barbutiric acid and thiazolidine-2,4-dione as electron acceptor. The effects of these three acceptors and length of alkyl on the performance of the DSSCs were investigated systematically along with their photophysical and photo electrochemical properties. These series of organic dyes include (B-CH, B-C B, DT-CB, DB-CB). Our investigation indicate among dyes containing butyl as... 

Perovskite solar cells (PSCs) use perovskites with an APbX3 structure, where A is a monovalent cation and X is a halide such as Cl, Br, and/or I. Currently, the cations for high-efficiency PSCs are Rb, Cs, methylammonium (MA), and/or formamidinium (FA). Molecules larger than FA, such as ethylammonium (EA), guanidinium (GA), and imidazolium (IA), are usually incompatible with photoactive “black”-phase perovskites. Here, novel molecular descriptors for larger molecular cations are introduced using a “globularity factor”, i.e., the discrepancy of the molecular shape and an ideal sphere. These cationic radii differ significantly from previous reports, showing that especially ethylammonium (EA)... 

Three new chromophores based on the triphenylamine (MM, DM, DN) with various novel electron withdrawing anchoring groups have been synthesized for use in dye-sensitized solar cells (DSSCs). The sensitizers were characterized by 1H and 13C NMR, Mass, UV–Vis, and electrochemical analysis. The HOMO and LUMO electron distributions of the sensitizers were calculated using density functional theory on a B3LYP level for geometry optimization. The DSSC device based on DM dye showed the best photovoltaic performance among MM and DN dyes: maximum monochromatic incident photon-to-current conversion efficiency (IPCE) of 98 %, short circuit current (JSC) of 4.58 mA/cm2, open circuit voltage (VOC) of... 

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... 

The identification of recombination centers in perovskite solar cells is highly challenging. Here, we demonstrate the red and blue excitation wavelength resolved impedance response in state-of-the-art perovskite solar cells (PSCs) providing insights into charge recombination and ion accumulation. To get insight into the interfacial electronic characteristics, we fabricated PSCs with a planar architecture containing state-of-the-art triple-cation perovskite materials as absorber layers. The capacitance-frequency response under various blue and red illumination conditions were used to investigate interfacial charge accumulations and found that under high energy photons irradiation maximum... 

In the current investigation, four novel donoracceptor type organic dyes including (DPA-Ba, DPA-Hy, DPA-Rh, DPA-Cy), are proposed and their photophysical and electrochemical properties as well as dye-sensitized solar cell performance are systematically investigated. Among these dyes diphenylamine is utilized as an-electron donor while barbituric acid, hydantoin, rhodanine-n-acetic acid and cyano acetic acid, are proposed as anchoring groups as dye-sensitized solar cells (DSSCs). The synthesized dyes are characterized using FT-IR, NMR, mass spectrometry, absorbance and electrochemical measurements. The photophysical, electrochemical and photovoltaic properties of the solar cells based on... 

Herein, we report a modified two-step method to construct a uniform and pinhole-free polycrystalline perovskite film with large grains up to the microscale using lead mixed-halide (PbI2-PbCl2) precursor solutions to guarantee the device functioning. Commonly used sequential deposition methods based on dip- and spin-coatings are combined with a vapor-assisted solution process to improve the perovskite morphology and tune the residual lead mixed-halides. These can enhance the optical absorption and efficiency of perovskite solar cell (PSC) devices. The impact of the Cl content in the lead mixed-halide precursors and the employed preparation methods on the photovoltaic performance of PSCs are... 

Perovskite solar cells (PSCs) have attracted significant attention due to their excellent efficiency reaching 22.1% in just the past few years. Despite their high efficiency, the limited long-term stability of PSCs has to be overcome. Moisture environments has been recognized as a main degradation pathway of perovskite materials. This review summarizes recent studies about relationship of the stability of PSCs with moisture environment. We also discuss the current standard strategies for enhancing the stability of PSCs by modifying the properties of either the perovskite material itself or its interfaces. © 2018  

In this research, inorganic copper thiocyanate (CuSCN) hole transport layer (HTL) was applied in conventional structure of perovskite solar cells (PSCs). Besides, mixed halides perovskite (Cs0.05(MA0.17FA0.83)0.95Pb(I0.83Br0.17)3) was utilized as the light absorbing layer and deposited on FTO/compact TiO2 substrates through a one-step coating method in ambient condition. The mentioned perovskite is more stable against high temperature, high irradiation and humidity compared to commonly applied MAPbI3 perovskite. Nevertheless, the CuSCN could not be well dissolved in usual dipropyl sulfide solution and should be deposited for several times to achieve suitable thickness, this could reduce the... 

Hole-transporter-free perovskite solar cells carrying a carbon back contact electrode provide the possibility of making full printable low cost and stable devices, even though their efficiency is substantially lower than those made in the standard configuration. The present work searched for simple and easy routes for constructing such devices, demonstrating that organic components do enhance device efficiency but only to a level that is not worth the trouble nor the cost. Devices based on a triple mesoporous layer of titania/zirconia/carbon with perovskite infiltration gave an efficiency of 10.7%. After 180 days of storing under ambient conditions, a small loss of efficiency has been... 

Perovskite solar cells (PSCs) have attracted significant attention due to their excellent efficiency reaching 22.1% in just the past few years. Despite their high efficiency, the limited long-term stability of PSCs has to be overcome. Moisture environments has been recognized as a main degradation pathway of perovskite materials. This review summarizes recent studies about relationship of the stability of PSCs with moisture environment. We also discuss the current standard strategies for enhancing the stability of PSCs by modifying the properties of either the perovskite material itself or its interfaces