Power Conversion Efficiency Of Dye-sensitized Solar Cells Research Articles

Natural rubber (Hevea Brasiliensis)-based quasi-solid electrolyte as a potential candidate for arresting recombination and improving performance in aqueous dye-sensitized solar cells

We successfully fabricated dye sensitized solar cells (DSSCs) employing a quasi-solid state electrolyte based on pristine insulator natural rubber latex from Hevea brasiliensis and iodide electrolyte. Optimized devices exhibited a maximum power conversion efficiency (PCE) of 1.14% under simulated sunlight with 90 mW/cm2 illumination, 0.46% under 100 mW/cm2 and 7.85% under low intensity illumination of 1000 lx (Daylight LED). This gives a new perspective for the introduction of natural rubber latex abundant in nature as an additive to the water based redox mediator in order to improve the PCE in DSSC. A detailed study on the interfacial charge transfer in fabricated devices revealed that the introduction of rubber helped in arresting the back electron transfer, which was predominant in aqueous electrolyte based dye sensitized solar cell. This opens up opportunities for water-based electrolyte based on natural raw materials to be used in nature inspired DSSC technology.

Low-Temperature Chemical Sintering Technique for Flexible Dye-Sensitized Solar Cells

Chemically sintered, mesoporous TiO2 electrodes were prepared at low-temperature (≤150 °C) using polymeric- binder free TiO2 paste consisting of binary-liquid mixture of 1-octanol and a series of chlorinated hydrocarbons (CHCs), such as carbon tetrachloride (CCl4), tetrachloroethylene (C2Cl4) or chloroform (CHCl3). In this work, CHCs were introduced to lower the boiling point of the mixture and to perform as an active agent for chemical treatment of TiO2 paste. Long chain alcohol 1-octanol increased the viscosity and diminished the surface tension of TiO2 paste to the hydrophobic surface of the substrate, which promoted the paste adhesion. A maximum power conversion efficiencies (PCEs) of c.a. 6.66 and 4.30% (under 1 sun illumination –100 mW cm-2) were obtained for the rigid dye-sensitized solar cells (DSSCs) with fluorine-doped tin oxide (FTO) and the flexible one with indium tin oxide-polyethylene naphthalate (ITO/PEN) substrates, respectively. Under LED daylight illumination, maximum PCEs of 10.10% at 3.39 mW cm-2 and 8.35% at 1.87 mW cm-2 have also achieved for DSSCs prepared on FTO substrate. The improved chemical bonding of particle network and strong adhesion to the substrates facilitated the electron transfer from TiO2 photoelectrodes to charge collectors, which played an important role for the significant enhancement of photocurrent density as well as PCE of DSSCs. The effect of CHCs on TiO2 is found to be a promising strategy to prepare well-connected TiO2 film for other applications.

Efficient charge collection of photoanodes and light absorption of photosensitizers: A review

During the recent period of time, dye sensitized solar cells (DSSCs) have become an exciting invention to meet our energy demands. Its reasonable cost of production and easy fabrication make it a powerful competent to the conventional solar cells. But non-achievement of expected efficiency is the key challenge faced by the scientific society. To overcome this, boundless research is going on the revamping of DSSC. Among the four chief parts of DSSC, the photoanodes gain more attention due to its dual function. Scilicet, it act as a charge carrier and as a surface for dye adsorption as well. Hence photoanode modification plays a crucial role in enhancing the power conversion efficiencies of DSSCs. It comprises of wide bandgap semiconducting metal oxides, among which TiO2 stands out with higher efficiency. Likewise in the case of photosensitizers, metal complex based dyes (mainly ruthenium based) take the lead in augmented efficiency. This paper critically reviews the work on all the metal oxides used as photoanode materials, comparing their band gap with the best efficiencies reported for each and analyzing their advantages and disadvantages. An overview of the performance of DSSCs based on different metal atom doped metal oxide photoanode, incorporation of various carbonaceous materials and different passivating agents has been included. Also, the modification in the photosensitizer has been discussed, examining the reports on organometallics based dyes and metal free organic dyes.

Nitrogen-doped carbon encapsulating γ-MoC/Ni nanoparticles as efficient counter electrodes for dye-sensitized solar cells

The counter electrode (CE) is a crucial part in dye-sensitized solar cells (DSSCs). By catalyzing the reduction of the oxidized state to the reduced state for a redox couple (e.g. I3 −/I−) in electrolyte, the CE fulfills the vital role of completing the electric circuit. Developing efficient and economical electrocatalytic materials to replace the traditional platinum (Pt) CE has attracted attention. In the present study, γ-MoC/Ni@NC material was used as a CE in DSSCs for the first time. This material was synthesized by solid-state pyrolysis of related compounds of molybdate, oxalate, melamine and nickel salts. The DSSC with this composite catalyst achieves power conversion efficiency (PCE) of 5.26%, which is equivalent to the one based on the traditional Pt CE (5.65%). Although the PCE of DSSC based on γ-MoC/Ni@NC is slightly lower than that of Pt, the synthesis method is simple and cost-effective. This study paves the way for further development of highly active, simple processing, inexpensive CE materials in DSSCs.

Effect of using betalain, anthocyanin and chlorophyll dyes together as a sensitizer on enhancing the efficiency of dye‐sensitized solar cell

The paper explored the mechanism of working of dye sensitizers for the improvement of efficiency of environmentally benign dye-sensitized solar cells (DSSC). The identified natural dyes namely anthocyanin (A), betalain (B) and chlorophyll (C) were extracted from Roselle (Hibiscus sabdariffa L.), spinach (Spinacia oleracea) and beetroot (Beta vulgaris) respectively. Light absorption performance of dyes was recorded by ultraviolet-visible (UV-vis) spectroscopic analysis followed by direct and indirect band gap calculation. The effect of functional groups present in the dyes studied by Fourier transform infrared spectroscopy (FTIR) and binding of the dyes on TiO2 through surface morphology of sheets was identified employing field emission scanning electron microscopy (FESEM). Photovoltage characteristics (I-V) and induced photon to current efficiency (IPCE) measurements were also noted followed by the stability studies. The N3 (synthetic dye chosen for the reference) dye-based cell showed the highest efficiency of 6.19% out of all of 11 cells fabricated using different sensitizers. The DSSC fabricated using the novel mixed dye (ABC) mixture gave the highest efficiency of 3.73%, however it showed similar drop (almost 22%) in efficiency as that with of N3 dye in stability studies. The mechanism for the increase in the overall power conversion efficiency of DSSC was also suggested.

Interfacial Charge-Transfer Transitions for Direct Charge-Separation Photovoltaics

Photoinduced charge separation (PCS) plays an essential role in various solar energy conversions such as photovoltaic conversion in solar cells. Usually, PCS in solar cells occurs stepwise via solar energy absorption by light absorbers (dyes, inorganic semiconductors, etc.) and the subsequent charge transfer at heterogeneous interfaces. Unfortunately, this two-step PCS occurs with a relatively large amount of the energy loss (at least ca. 0.3 eV). Hence, the exploration of a new PCS mechanism to minimize the energy loss is a high-priority subject to realize efficient solar energy conversion. Interfacial charge-transfer transitions (ICTTs) enable direct PCS at heterogeneous interfaces without energy loss, in principle. Recently, several progresses have been reported for ICTT at organic-inorganic semiconductor interfaces by our group. First of all, new organic-metal oxide complexes have been developed with various organic and metal-oxide semiconductors for ICTT. Through the vigorous material development and fundamental research of ICTT, we successfully demonstrated efficient photovoltaic conversion due to ICTT for the first time. In addition, we revealed that the efficient photoelectric conversion results from the suppression of charge recombination, providing a theoretical guiding principle to control the charge recombination rate in the ICTT system. These results open up a way to the development of ICTT-based photovoltaic cells. Moreover, we showed the important role of ICTT in the reported efficient dye-sensitized solar cells (DSSCs) with carboxy-anchor dyes, particularly, in the solar energy absorption in the near IR region. This result indicates that the combination of dye sensitization and ICTT would lead to the further enhancement of the power conversion efficiency of DSSC. In this feature article, we review the recent progresses of ICTT and its application in solar cells.

A Novel Single-Atom Electrocatalyst Ti1 /rGO for Efficient Cathodic Reduction in Hybrid Photovoltaics.

Single-atom catalysts (SACs) are a frontier research topic in the catalysis community. Carbon materials decorated with atomically dispersed Ti are theoretically predicted with many attractive applications. However, such material has not been achieved so far. Herein, a Ti-based SAC, consisting of isolated Ti anchored by oxygen atoms on reduced graphene oxide (rGO) (termed as Ti1 /rGO), is successfully synthesized. The structure of Ti1 /rGO is characterized by high-angle annular dark-field scanning transmission electron microscopy and X-ray absorption fine structure spectroscopy, being determined to have a five coordinated local structure TiO5 . When serving as non-Pt cathode material in dye-sensitized solar cells (DSCs), Ti1 /rGO exhibits high electrocatalytic activity toward the tri-iodide reduction reaction. The power conversion efficiency of DSCs based on Ti1 /rGO is comparable to that using conventional Pt cathode. The unique structure of TiO5 moieties and the crucial role of atomically dispersed Ti in Ti1 /rGO are well understood by experiments and density functional theory calculations. This emerging material shows potential applications in energy conversion and storage devices.

Balance between the explored Pt counter electrode in an electrolyte medium and the photoanode for highly efficient liquid-junction photovoltaic devices

Abstract This work investigates the effect of the ratio of the explored Pt area in the electrolyte medium and the photoanode area (REP) on the performance of dye-sensitized solar cells (DSCs). It is found that the power conversion efficiency of DSCs increases by the ascending REP. The highest power conversion efficiency, which was obtained for the cell with the REP of 64/49, was 8.40%. Furthermore, a relationship between the efficiency and fabrication cost is analyzed in terms of reducing or enhancing the surface area of CE compared to the photoanode's surface area. These findings may provide a way for the development of efficient and large-scale DSCs.

Platinum leaf counter electrodes for dye-sensitized solar cells

In this study, a platinum (Pt) leaf was introduced as a counter electrode (CE) with thickness of 100 nm in dye-sensitized solar cells (DSCs). Fundamental characteristics were investigated and compared with Pt leaf, Pt plate, and sputtered-Pt as the CEs. The power conversion efficiencies of DSCs with a Pt leaf as the CEs were as high as 4.78%, which is higher to those of DSCs with Pt plate and sputtered-Pt as the CEs (4.11% and 4.40%, respectively). In contrast to other CEs, Pt leaf features a large surface area. This implies that Pt leaf serves as an active CE and can be a good candidate for DSCs.

White Painting Pigment as a Low-Cost Light Scattering Material for Bilayer Photoelectrodes of Dye-Sensitized Solar Cells

White pigment (DuPont R902+) has been used as a light scattering material in the preparation of bilayerphotoelectrodes of dye-sensitized solar cells (DSCs). The X-ray diffraction (XRD) pattern of the white pigment revealed that the material consists of rutile phase of titanium dioxide. The light scattering layer prepared from the white pigment was coated onto the main-layer of the photo electrodes of DSCs. The solar cells with and without light scattering layer were tested in the simulated light of 100 mW/cm2. The DSCs with the light scattering layer generated more current density than the DSCs without scattering layer and the overall light to electric power conversion efficiency of DSCs with the light scattering layer was ~4.00 % compared with 3.25 % efficiency of the DSCs without the scattering layer.

Transforming polymorphs of Co-doped TiO2 nanoparticles: an efficient photo-electrode for dye-sensitized solar cells

Simple sol–gel assisted spin coating technique was used to prepare cobalt-doped TiO2 films for the application of dye-sensitized solar cells (DSSC). TiO2 photo-electrodes with few Co concentrations (0, 0.025, 0.05, 0.075 and 0.1 M) were prepared on conducting glass substrates. The morphology, structure and composition of the Co:TiO2 films were observed using SEM, XRD and EDAX analysis. The average crystallite size of Co:TiO2 nanoparticles obtained from diffractograms are in the range of 3–12 nm. The transformation of polymorphs from anatase to rutile and vice versa for the increasing concentrations of Co in TiO2 films is observed. The values of optical bandgap energy for Co-doped films are observed to be higher than the pure TiO2 film and the highest is for the dopant level of 0.025 M. Doping of 0.1 M Co in TiO2 enhances the power conversion efficiency of DSSC by 65% compared to pure TiO2 film, demonstrating the influence of Co doping on the functioning of DSSC.

Surface Carbon Shell-Functionalized ZrO2 as Nanofiller in Polymer Gel Electrolyte-Based Dye-Sensitized Solar Cells.

We prepare dye-sensitized solar cells (DSSCs) fabricated with a poly (ethylene glycol) based polymer gel electrolytes (PGEs) incorporating surface carbon shell-functionalized ZrO2 nanoparticles (ZrO2-C) as nanofillers (NFs). ZrO2 are polymerized via atom transfer radical polymerization (ATRP) using poly (ethylene glycol) methyl ether methacrylate (POEM) as a scaffold to prepare the ZrO2-C through carbonization. The power conversion efficiency of DSSC with 12 wt% ZrO2-C/PGEs is 5.6%, exceeding that with PGEs (4.4%). The enhanced efficiency is attributed to Lewis acid-base interactions of ZrO2-C and poly (ethylene glycol), catalytic effect of the carbon shells of ZrO2-C, which results in reduced crystallinity, enhanced ion conductivity of electrolytes, decreased counterelectrode/electrolyte interfacial resistance, and improved charge transfer rate. These results demonstrate that ZrO2-C introduction to PGEs effectively improves the performance of DSSCs.

Post-treatment of Nb2O5 compact layer in dye-sensitized solar cells for low-level lighting applications

Introduction of an ultrathin compact layer in dye-sensitized solar cells (DSSCs) can improve the cell efficiency under standard one sun illumination (> 100,000 lx). Herein, an ultrathin Nb2O5 layer is deposited on the TiO2-coated photoanode using a facial dip-coating method and its effects on the cell efficiency under a low level of light intensity (300–6000 lx) is studied. The results show that the ultrathin Nb2O5 layer helps the DSSCs to improve their power conversion efficiency (PCE) through different ways under standard one sun and low power illuminations. Under strong one sun illumination, the PCE of DSSC is improved by improving the short-circuit current density (JSC) which can be attributed to an increment of the surface area of photoanode for more dye adsorption and the blocking effect of Nb2O5. Under low power illumination, the introduction of Nb2O5 blocking layer improves the fill factor by effectively suppressing the charge recombination on the photoanode.

Demagnetization field driven charge transport in a TiO2 based dye sensitized solar cell

We report on the effect of demagnetizing fields due to magnetite (Fe3O4) nanoparticles (NPs) on the efficiency of TiO2 based dye sensitized solar cells (DSSC). The addition of Fe3O4 NPs into the photoanode enhanced the power conversion efficiency of DSSC. This may be attributed to the magnetic field effect induced by the demagnetizing field produced by the magnetite NPs, which is evident from our micromagnetic simulation. Essentially, such a stray field would induce additional force on the electron motion and thereby enhancing the recombination time of these charge carriers. Enhancement in recombination time is directly evidenced by the increase in short circuit current density. In addition, we have carried out an electrochemical impedance spectroscopy (EIS) study to probe the mechanism of charge transport within the DSSC device. Quenching of intensity in phosphorescence data indeed infer a decrease in recombination rate. We calculated the value of demagnetization energy from NPs with micromagnetic simulations. Absorbed energy density of ‘s’ and ‘p’ polarized incident light estimated using transfer matrix model.

Comparison of mono- and di-substituted triphenylamine and carbazole based sensitizers @(TiO2)38 cluster for dye-sensitized solar cells applications

This study has been performed to understand the effect of donor strength on photovoltaic performance of Dye-sensitized Solar Cells (DSSCs). For this purpose, Density Functional Theory (DFT) and time domain DFT calculations were carried out. The results reveal that triphenylamine based Dye 2 and carbazole based Dye 4 with di-substituted donor moieties showed red shifted absorption wavelengths, higher oscillator strength and improved electron injection leading to the larger short-circuit photocurrent density (JSC). It is expected that these dyes might show larger open-circuit photovoltage (VOC) as well. These results disclose that di-substitution of the donor moiety would be an efficient strategy to enhance JSC and VOC for better light to power conversion efficiency in DSSCs.

Cosensitization in Dye-Sensitized Solar Cells.

Dye-sensitized solar cells (DSCs) are a next-generation photovoltaic technology, whose natural transparency and good photovoltaic output under ambient light conditions afford them niche applications in solar-powered windows and interior design for energy-sustainable buildings. Their ability to be fabricated on flexible substrates, or as fibers, also makes them attractive as passive energy harvesters in wearable devices and textiles. Cosensitization has emerged as a method that affords efficiency gains in DSCs, being most celebrated via its role in nudging power conversion efficiencies of DSCs to reach world-record values; yet, cosensitization has a much wider potential for applications, as this review will show. Cosensitization is a chemical fabrication method that produces DSC working electrodes that contain two or more different dyes with complementary optical absorption characteristics. Dye combinations that collectively afford a panchromatic absorption spectrum emulating that of the solar emission spectrum are ideal, given that such combinations use all available sunlight. This review classifies existing cosensitization efforts into seven distinct ways that dyes have been combined in order to generate panchromatic DSCs. Seven cognate molecular-engineering strategies for cosensitization are thereby developed, which tailor optical absorption toward optimal DSC-device function.

Synthesis of carbon nanofiber based WO3/TiO2 hybrid nanostructures: Enhanced and improved solar conversion efficiency in dye-sensitized solar cell

Dye-sensitized solar cells (DSSCs), which are new generation solar cells, are designed by using carbon nanofiber (CNF) based WO3/TiO2 nanostructures. CNF/WO3/TiO2 nanosemiconductors can be used as photoanodes in DSSCs. It has been indicated that CNF/WO3/TiO2 is a promising alternative to standard DSSCs due to their highly porous surface area and perfect optoelectronic properties. The uses of CNF/WO3/TiO2 hybrid structures provided an improvement to the performance of devices. DSSCs based on CNF/WO3/TiO2 hybrid structures exhibited a power-conversion efficiency (PCE) of 7.28%. It was shown that enhanced light absorption prevents recombination and the perfect accord work function of the hybrid structures gives a high solar conversion efficiency. The enhancements of the PCE in DSSCs originate from the increase in photovoltage with the improvement of the fill factor (FF). The increase in Voc was caused by the increase in the dye adsorption on the substrate and the enhancement of FF which was attributed to faster electron transportation on the devices. It was shown that the CNF/WO3/TiO2 nanostructures had large surface areas, highly nanoporous structures (below 20 nm), and excellent work functions between CNF/WO3 nanoparticles and TiO2 anatase. It was also demonstrated that the new material CNF/WO3/TiO2 nanostructures displayed a wide scan scale photon absorption and exhibited the highest photovoltaic performance.

The preparation of dye sensitized solar cells using natural dyes extracted from Phytolacca icosandra and Phyllanthus reticulatus with ZnO as photoanode

Dye sensitized solar cells are promising class of photovoltaic cells with the capability of generating green energy at low production cost since no expensive equipment is required in their fabrication. Zinc oxide (ZnO) nanorods were synthesized by hydrothermal method and their performance as photoanodes in dye sensitized solar cells (DSSCs) with dye extracts from fruits of Phytolacca icosandra and Phyllanthus reticulatus as sensitizers was analyzed. Detailed structural and surface characterization of the ZnO nanorods were accomplished using X-ray diffraction (XRD) analysis and high resolution scanning electron microscopy (HRSEM). XRD results revealed that the synthesized ZnO material exhibited hexagonal crystal structure which was found to be highly stable and crystallite. The dye extracts were subjected to UV–Visible absorption spectroscopy and Fourier Transform Infrared (FTIR) analysis. The short-circuit photocurrent; the open-circuit photovoltage, and the power conversion efficiency of DSSC were measured using J-V measurement system.

Natural Dyes Extracted from Fruits of Phyllanthus reticulatus as Sensitizers in ZnO Nanorods Based Dye Sensitized Solar Cells

DSSCs are a promising class of photovoltaic cells with the capability of generating green energy at low production cost since no expensive equipment is required in their fabrication. Zinc oxide (ZnO) nanorods were synthesized by hydrothermal method and their perfomance as photoanodes in dye-sensitized solar cells (DSSCs) employing I-/I3- as electrolyte and the dye extracts from fruits of Phyllanthus reticulatus as sensitizers was analyzed. the structural and surface characterization of the ZnO nanorods were accomplished using X- ray diffraction (XRD) analysis and high resolution scanning electron microscopy (HRSEM). XRD results revealed that the synthesized ZnO material exhibited hexagonal crystal structure which was found to be highly stable and crystallite. The dielectric properties of the ZnO nanorods were analyzed. The dye extracts were subjected to UV-Visible absorption spectroscopy analysis. The short-circuit photocurrent, the open-circuit photovoltage, and the power conversion efficiency of DSSC were measured using J-V measurement system.

Fabrication of conductive and printable nano carbon ink for wearable electronic and heating fabrics

Printable Nano carbon colloidal ink has fascinated great attention due to their exceptional potential for large-scale application for powering wearable electronic devices. Though, it is challenging to incorporate various characteristics together such as mechanical stability, solution printability, conductivity, electrocatalytic activity, and heat generating properties in the flexible fabric based electrode system. In this research the development of printable composites made with woven/nonwoven fabrics printed with multiwall carbon nanotubes for flexible and wearable heating system and cathodes for dye-sensitized solar cells (DSSC), respectively. We report a printable carbon ink of multiwall carbon nanotubes (MWCNT) synthesized by globular protein serum bovine albumin (BSA). BSA is amino-rich dispersant used to disperse MWCNT and generate tubular porous carbon matrix. High loading ratio of BSA increases the dispersing power of MWCNT and increased porosity of CNT matrix. The proposed Organic Nanocarbon ink (Organic NC) serve the pathways for electron transport leading to higher heat dissipation as the well high conductivity and electrocatalytic activity. It was interesting to reveal that different kinds of woven and nonwoven fabrics displayed exceptional thermal properties when DC voltage was applied. The heat generating properties were highly dependent on the type of fabric and conductive ink uptake. Our proposed Organic NC printed fabric system exhibited superior conductivity with 15–20 Ω resistivity and lower charge transfer resistance RCT = 2.69 Ω, demonstrated an 8% power conversion efficiency of DSSC. The proposed research paves the ways for solution printable high performance woven and nonwoven conductive and thermoelectric materials for wearable electronics.