Third-Generation-Sensitized Solar Cells

The need to produce renewable energy with low production cost is indispensable in making the dream of avoiding undue reliance on non-renewable energy a reality. The emergence of a third-generation photovoltaic technology that is still in the infant stage gives hope for such a dream. Solar cells sensitized by dyes, quantum dots and perovskites are considered to be third-generation technological devices. This research focuses on the development of suitable and reliable sensitizers to widen electromagnetic (EM) wave absorption and to ensure stability of the photovoltaic system. This article discusses the basic principles and the progress in sensitized photovoltaics

Plasmonic Effect in Photoelectrochemical Cells

Two types of third-generation photovoltaic (PV) cells are sensitized by dyes and quantum dots (QDs), the former being dye-sensitized solar cell abbreviated as DSSC. The second is the quantum dot-sensitized solar cell or QDSSC. There are three main components in DSSC and QDSSC. The photoanode is the component where the light is being absorbed either by molecules of the dye or by the quantum dots (QDs). The sensitizers are attached on the semiconductor (normally TiO2) surface. The conduction band (CB) of the semiconducting material should be at a level lower than the lowest unoccupied molecular orbital (LUMO) of the dye molecules or CB of QDs for fast electron transfer. Incorporation of plasmonic materials into the photoanode can increase light absorption efficiency by surface plasmon effect and thus improve the efficiency of the DSSCs and QDSSCs. Plasmonic materials that have been employed include gold (Au), silver (Ag) and aluminum (Al) nanoparticles (NPs). Different NPs exhibit different effects on the cell parameters. Covering the NPs with a thin wide bandgap semiconducting film is necessary to protect the plasmonic NP materials from the corrosive nature of the electrolyte

Application of LiBOB-based liquid electrolyte in co-sensitized solar cell

Co-sensitized solar cells have been fabricated using metal complex N3 dye and Ag2S/CdS quantum dots coupled with LiBOB-based liquid electrolyte. Quantum dots (QDs) were synthesized via the successive ionic layer adsorption and reaction (SILAR) route. The absorbance and band gap energy of Ag2S and CdS QDs were determined. Their refractive indices were observed to be in the range of 1.5175-1.5200. It has been shown that LiBOB-based liquid electrolyte is able to function in the QD/N3 dye co-sensitized solar:cells but some stability issues of the QD were observed in the electrolyte system containing iodide whereby the QD-sensitized TiO2 was easily etched. Overall efficiencies and fill factors of the co-sensitized solar cells varied from 0.98% to 1.66% and 40% to 46% respectively. CdS QD was shown to be effective when coupled with polysulfide electrolyte while Ag2S QD was favorable towards the LiBOB-based liquid electrolyte

Impact of tetrabutylammonium, iodide and triiodide ions conductivity in polyacrylonitrile based electrolyte on DSSC performance

Gel polymer electrolytes (GPEs) with polyacrylonitrile (PAN)-based polymer, ethylene carbonate (EC) and propylene carbonate (PC) plasticizers, and different amounts of tetrabutylammonium iodide (TBAI) salt and iodine (I2) have been prepared and used in dye-sensitized solar cells (DSSCs). The maximum room temperature conductivity of 5.14 mS cm−1 is obtained for electrolyte with a composition of 8 wt% PAN-30 wt% EC-30 wt% PC-30 wt% TBAI-2 wt% I2 (S3 electrolyte) which influenced by the highest charge carrier density of 7.93 × 1020 cm−3 estimated from fitting the impedance Nyquist plot. The DSSC fabricated with S3 electrolyte revealed the highest power conversion efficiency of 3.45% with open-circuit voltage (Voc) of 582 mV and short-circuit current density (Jsc) of 12.9 mA cm−2. The incident photon-to-current conversion efficiency of the DSSC with highest efficiency is 54.01%. The electrical impedance spectroscopy of the same cell shows the lowest series resistance indicating the superiority of electrolyte charge transport characteristics in DSSC. In addition, electron transfer time constant and electron recombination time , charge collection efficiency , electron diffusion coefficient and diffusion length of DSSC fabricated with GPEs prepared have been estimated by intensity-modulated photocurrent spectroscopy and intensity-modulated photovoltage spectroscopy techniques. The DSSC with highest efficiency shows lowest of 34.46 ms and highest of 90.41 ms due to the huge amount of TBA+ ions that covered the surface area of mesoporous TiO2. The of 0.62, D of 4.00 × 10−5 cm2 s−1 and of 19.02 μm further support the photovoltaic efficiency of DSSC

Polyacrylonitrile gel polymer electrolyte based dye sensitized solar cells for a prototype solar panel

Polyacrylonitrile (PAN) based gel polymer electrolytes (GPE) were prepared using lithium iodide (LiI), 1-butyl-3-methylimidazolium iodide (BMII) and tetrapropyl ammonium iodide (TPAI). The LiI mass fraction in the electrolyte was varied while keeping the masses of other components constant in order to enhance the solar cell performance. The addition of 4.61 wt.% LiI in the GPE increased the electrolyte room temperature ionic conductivity from (2.32 ± 0.02) to (3.91 ± 0.04) mS cm−1. The increase in conductivity with the addition of LiI salts was attributed to the increase in diffusion coefficient, mobility and number density of charge carriers as determined from Nyquist plot fitting. The incorporation of LiI salts in PAN-based GPE has enhanced the efficiency of the DSSC as expected. The best cell performance was obtained with an electrolyte containing 4.61 wt.% LiI sandwiched between a single mesoporous layer of TiO2 soaked in N3 dye sensitizer and a platinum counter electrode, which showed a power conversion efficiency (PCE) of (5.4 ± 0.1) % with a short circuit current density (Jsc) of (21.0 ± 1.1) mA cm−2, an open circuit voltage (Voc) of (0.48 ± 0.02) V and a fill factor (FF) of (53.4 ± 0.9) %. The DSSCs with 4.61 wt.% of LiI have been used to fabricate prototype solar panels for operating small devices. The panels were assembled using a number of cells, each having an area of 2 cm × 2 cm, connected in series and parallel. The panel, consisting of a set of eight cells in series which was connected in parallel with another set of eight cells in series, produces an average power conversion efficiency of (3.7 ± 0.2)% with a maximum output power of (17.1 ± 0.9) mW

Improvement of dye sensitized solar cells efficiency utilizing diethyl carbonate in PVA based gel polymer electrolytes

Low conductivity of gel polymer electrolytes (GPEs) containing double iodide salts is critical for efficiency in dye-sensitized solar cells (DSSCs). The presence of diethyl carbonate (DEC) plasticizer affects the amorphousness and ionic conductivity of polyvinyl alcohol (PVA)-based GPEs and DSSCs performance. In this work, PVA-based GPEs containing a variation of DEC have been produced, characterized, and applied in the DSSCs fabrication. The structural properties of GPEs were analyzed using X-ray diffraction (XRD). The ionic conductivity was determined from electrical impedance spectroscopy (EIS). Based on XRD, GPEs for all prepared compositions have been identified as an amorphous phase. From the EIS measurement, it was found that GPE with the composition of 5.46 PVA - 8.19 EC - 10.92 PC - 60.06 DMSO - 5.73 TPAI - 5.73 KI - 1.34 I2 - 2.57 DEC (in wt. %) having highest conductivity of 11.19 ± 0.20 mS cm-1 with activation energy, Ea of 0.09 eV. The graph of conductivity versus temperature following the Arrhenius rule has been plotted. The GPEs dominate the highest conductive with 2.57% of DEC and showed the DSSCs efficiency of 6.42%. Common DSSCs parameters resulted in short-circuit current density (Jsc) of 17.58 mA cm-2, fill factor (ff) of 0.63, and open-circuit voltage (Voc) of 0.58 V. In conclusion, DEC improves the ionic conductivity as well as amorphous properties of the GPE, and therefore enhance the DSSCs' efficiency

Chitosan: poly (vinyl) alcohol composite alkaline membrane incorporating organic ionomers and layered silicate materials into a PEM electrochemical reactor

Mixed matrix membranes (MMM) are prepared from equivalent blends of poly (vinyl alcohol) (PVA) and chitosan (CS) polymers doped with organic ionomers 4VP and AS4, or inorganic layered titanosilicate AM-4 and stannosilicate UZAR-S3, by solution casting to improve the mechanical and thermal properties, hydroxide conductivity and alcohol barrier effect to reduce the crossover. The structural properties, thermal stability, hydrolytic stability, transport and ionic properties of the prepared composite membranes were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), water uptake, water content, alcohol permeability, thickness, ion exchange capacity (IEC) and OH- conductivity measurements. The addition of both organic and inorganic fillers in a CS:PVA blend polymer enhances the thermal and ionic properties. All the membranes are homogenous, as revealed by the SEM and XRD studies, except when UZAR-S3 stannosilicate is used as filler, which leads to a dual layer structure, a top layer of UZAR-S3 lamellar particles bound together by the polymer matrix and a bottom layer composed mostly of polymer blend. The loss of crystallinity was especially remarkable in 4VP/CS:PVA membrane. Thus, the 4VP/CS:PVA membrane exhibits the best ionic conductivity, whereas the UZAR-S3/CS:PVA membrane the best reduced alcohol crossover. Finally, the performance of the CS:PVA-based membranes were tested in a Polymer Electrolyte Membrane Electrochemical Reactor (PEMER) for the feasibility use of alkaline anionic exchange membranes in electrosynthesis under alkaline conditions, showing the 4VP/CS:PVA and UZAR-S3/CS:PVA membranes the best performances in PEMER.We gratefully acknowledge the financial support from the Spanish Ministry of Economy and Competitiveness (MINECO) for CTQ2012-31229 project at the University of Cantabria, and MINECO-FEDER (Fondo Europeo de Desarrollo Regional (2014- 2020) through the CTQ2013-48280-C3-3-R project at the University of Alicante. C. C. C. also thanks the MINECO for the “Ramón y Cajal” program at the University of Cantabria (RYC2011-08550), and L. G. C. for her PhD fellowship BES-2011-045147 and the EEBB- 14-09094 mobility grant for the research stay at the University of Cantabria, respectively. Dr. César Rubio, Prof. Carlos Téllez and Prof. Joaquín Coronas from the University of Zaragoza are also warmly thanked for the UZAR-S3 sample

PENGARUH MODEL PEMBELAJARAN CONNECTED MATHEMATICS PROJECT (CMP) BERBANTUAN GOOGLE SITE TERHADAP KEMAMPUAN PEMAHAMAN KONSEP MATEMATIS

The purpose of this study was to analyze the ability to understand mathematical concepts of students who were taught with the Google Site-assisted CMP learning model better than those taught with the direct learning model. The next objective is to analyze the ability to improve understanding of mathematical concepts taught with the Google Site-assisted CMP learning model for derived material. This research is quantitative research with quasi-experimental design. The nonequivalent control group design was used as a form of quasi-experimental, by comparing two samples of 44 students from class XI MIPA SMA Negeri 2 Magelang who were randomly selected. From the Independent Sample t-Test test it produces a value of  then  is rejected and  is accepted which means the ability to understand mathematical concepts taught with the Google Site-assisted CMP learning model is better than the direct learning model. Then, the average N-Gain test was 0.38 and proved that there was an increase taught by the Google Site-assisted CMP learning model for derivative material in the medium category. From the results of hypothesis testing, it can be concluded that the ability to understand mathematical concepts taught by the Google Site-assisted CMP learning model is better than the direct learning model for derivative material, and there is an increase in the moderate category

Ionic conductivity and related studies on chitosan-based electrolytes with application in solar cells / Mohd Hamdi Ali@Buraidah

The motivation in this work is to ensure that the chitosan biopolymer can be used as a host for ion conduction and used as an electrolyte in dye-sensitized solar cells (DSSCs). The conductivity of the chitosan-NH4I electrolytes was optimized by varying the NH4I concentration, blending chitosan with PVA and PEO and also by incorporating of ionic liquid (IL). The electrolytes were prepared by solution cast technique. FTIR results confirm complexation between polymer, NH4I and IL. Hydrogen bonding between chitosan and PVA and between chitosan and PEO are observed in the respective spectrum. XRD indicates that the amorphousness of pure chitosan, chitosan-PVA and chitosan-PEO films changes with NH4I concentration. The 55 wt.% chitosan-45 wt.% NH4I (Ch9) sample exhibits the highest room temperature conductivity of 3.73 × 10-7 S cm-1. Blending chitosan with PVA and PEO further increased conductivity. The 27.5 wt.% chitosan-27.5 wt.% PVA-45 wt.% NH4I (CV5) sample exhibits the highest conductivity of 1.77 × 10-7 S cm-1 at room temperature and the highest conducting sample in (chitosan-PEO)-NH4I system is 3.66 × 10-6 S cm-1 for sample containing 16.5 wt.% chitosan-38.5 wt.% PEO-45 wt.% NH4I (CEO7) electrolyte. Incorporating 50 wt.% IL into Ch9, the electrolyte CIL5 exhibits the highest room temperature conductivity of 3.43 × 10-5 S cm-1. The activation energy, EA for the highest conducting samples follows the order Ch9 (0.45 eV) < CV5 (0.38 eV) < CEO7 (0.31 eV) < CIL5 (0.25 eV). DSSCs were fabricated using natural dyes extracted from black rice, blueberry and red cabbage. The highest conducting samples from each system have been chosen in the fabrication DSSCs. Some iodine crystals were added to the electrolytes to produce the redox-mediator. Red cabbage DSSCs using CIL5(+I2) gel electrolyte exhibits the highest efficiency of 0.2 % compared to using CEO7(+I2) and CV5(+I2) gel electrolytes

A novel LiSnVO4 anode material for lithium-ion batteries

In this work, a new material LiSnVO4 has been prepared via sol-gel method utilizing ammonium metavanadate, acetates of tin and lithium as starting materials, and nitric acid and oxalic acid as complexing agents. The amount of starting materials used has been chosen so that the mole ratio of Li/Sn/V is 1:1:1. The sol-gel precursor has been sintered at 700 °C for 6 h. Based on thermogravimetry analysis (TGA) analysis, the formation mechanism suggested the product to be LiSnVO4. Energy-dispersive X-ray analysis (EDX) reveals the ~1:1 ratio of Sn:V. EDX results agree reasonably with the formation mechanism from TGA analysis that the Sn:V ratio is 1:1. Results from X-ray photoelectron spectroscopy (XPS) indicate that the oxidation states of Li, Sn, and V are +1, +2, and +5, respectively. Since there is no ICDD data available to match the XRD diffractogram of the material obtained, CMPR and powder diffraction data interpretation and indexing program (POWD) softwares have been used to predict the crystal structure system to be tetragonal (similar to that of SnO2). A fabricated LiSnVO4//Li cell can deliver a large initial irreversible discharge capacity of 1270 mAh g−1 and reversible capacity of 305.4 mAh g−1 at the end of second cycle, which drops to 211 mAh g−1 at the end of 53rd cycle. The capacity retention is 69 % with respect to the second discharge capacity