what is meant by dye sensitized solar cell

A dye-sensitized solar cell(DSSC

, DSC, DYSCor Grätzel cell) is a low-cost solar cellbelonging to the group of thin film solar cells. It is based on a semiconductorformed between a photo-sensitized anode and an electrolyte, a photoelectrochemicalsystem.

Full Answer

What is a dye sensitized solar cell (DSSC)?

The dye sensitized solar cell, also known as DSSC or DSC, is a distinct type of photovoltaic (pv) cell which can effectively convert natural and artificial visible light into electrical energy. This new class of advanced solar cell mimics the natural absorption of light energy.

What is a dye-sensitized solar cell?

Dye-sensitized solar cells (DSSCs) are photovoltaic devices that are used to convert light energy into electrical energy by the use of organic dyes (photosensitizers) and semiconductors. They prove to the most economical and sustainable power supply for MEC applications because solar energy is the most abundant form of renewable energy.

Are solar cells more efficient than dye sensitized solar panels?

Although silicon solar cells are more efficient than dye sensitized solar cells, the former is essential as it can generate electricity in low light conditions. These solar cells can produce electricity even in indoor lights. Furthermore, these solar cells have a simple design and come at economical pricing.

What are the main parts of single junction dye sensitized solar cell?

The main parts of single junction dye sensitized solar cell are illustrated schematically in Figure 2. The cell is composed of four elements, namely, the transparent conducting and counter conducting electrodes, the nanostructured wide bandgap semiconducting layer, the dye molecules (sensitizer), and the electrolyte.

How Do Dye Sensitized Solar Cells Work?

The working mechanism of DSC differs greatly from other types of solar cells.

What does dye do in photosynthesis?

The dye uses energy from these photons to excite electrons in the cell, behaving like chlorophyll in photosynthesis.

What happens when a chemical electrolyte closes the circuit?

The chemical electrolyte in the cell closes the circuit so that the electrons are returned back to the dye.

Why is open circuit voltage high?

High open-circuit voltage because the organic p-type semiconductor has an energy level deeper than that of iodine

Do DSSCs degrade?

Compared to thin-film cells, DSSCs do not degrade in sunlight over time. Thus, dye sensitized solar cells last longer and require less frequent replacements. DSSCs are also mechanically strong, because they are made of lightweight materials and do not require special protection from rain or abrasive objects.

How do dye sensitized solar cells work?

11. It relies on the visible photoexcitation of dyes triggering an electron transfer into the conduction band of the metal oxide semiconductor (generally TiO 2) (equation I and II), followed by regeneration of the oxidized dye molecules by the electron donation from the redox couple in the electrolyte (equation III and IV) and finally migration of electron through the external load to complete the circuit ( Grätzel, 2000 ). The entire operation takes place with the help of different components of DSSC, such as the light-absorber (dye/sensitizer), the electron-transport agent (wide bandgap nanocrystalline semiconductor), and the hole-transport agent (redox couple in electrolyte). For successful conversion of sunlight to electrical power, all the components constituting the system should effectively play their role. Sensitizer/dye in particular should possess certain important features for efficient performance, namely, a broad and strong absorption from visible to near-infrared region, chemical stability of the appropriate lowest unoccupied molecular orbital and highest occupied molecular orbital levels for effective charge injection into the semiconductor, dye regeneration from the electrolyte, high-molar extinction coefficients in the visible, near-infrared region for light-harvesting, good photostability, and solubility to hamper the recombination.

Why are DSSCs bad?

Due to the use of liquid electrolytes, cells with DSSC technology have thermal stability problems. At low temperatures the electrolytes may freeze, blocking the production of power and potentially causing physical damage. In contrast, high temperatures cause the expansion of the liquid, making the sealing of modules difficult. In addition, the electrolyte solutions contain volatile organic compounds, harmful to humans, requiring special care in sealing to prevent leakage due to galvanic corrosion. Replacing the liquid electrolyte with a solid one (solid-state DSSCs—ss-DSSCs) has been a major focus of research so far, since the use of a solid electrolyte eliminates these problems but decreases the efficiency of total conversion.

What is DSSC in electronics?

A DSSC involves a porous layer of the oxide semiconductor (the anode, i.e., the negative electrode) nanoparticles, with the nanoparti cles being coated with a molecular dye (e.g., a ruthenium-based complex), such that the nanoparticles are electrically in contact with one another to form a continuous conductive path (percolation).

What is reaction 5 and 6?

Reaction 5 and 6: Recombination of Electrons in the Semiconductor with Oxidized Dyes or Electrolyte Species 407

How are anode and cathode separated?

Anode and cathode are separated by a liquid electrolyte based on organic compounds. The photons pass through the electrode and hit the photosensitive pigments, exciting the electrons until they transfer to the titanium anode and are extracted, generating electrical current. The electrolyte, after extracting return electrons from the cathode, refurnishes the dye with the electron it has just lost to the TiO 2, allowing the dye solar cell to transform sunlight continually into electric current.

What is a DSSC?

A dye-sensitized solar cell (DSSC) is an economical solar cell that comes in the category of thin-film solar cells. The DSSC has various striking merits: easy fabrication using the roll-to-roll technique as well as an economical and environmentally friendly nature, in the case of natural dyes. DSSC cells are designed and fabricated using four natural dyes: Celosia Cristata, Saffron, Cynoglossum, and eggplant peel. A maximum energy conversion efficiency of 1.38% was achieved by DSSC using Celosia Cristata as dye with a maximum absorbance of 510 nm as shown in Fig. 2.16 [39].

What is a DSC solar cell?

DSC, as a third-generation solar cell technology, is a potential low-cost candidate to meet the increasing energy demand in the world . Since the first reports on this technology appeared, about 18,000 research articles have been published. These researches are focused on low-cost mass production of highly efficient, stable, flexible solar cells. In this regard, polymer-based composite materials used in flexible DSCs, their production methods, and effects on performance were reviewed in this chapter.

How are DSSC and NG integrated?

DSSC, SC and NG can be integrated simultaneously on a single microsized fiber to realize solar and mechanical energy harvesting and subsequent storing, as presented in Fig. 16.3 [32]. NG, SC, and DSSC share a common substrate made from Au-coated polymethylmethacrylate (PMMA) fiber of diameter B220 mm. The Au layer serves as the common inner electrode. As an active piezoelectric material for NG, ZnO nanowires (NWs) were radially grown on the fiber. This ZnO layer also acts as a core material of the DSSC and also provides a large surface area for SC. As for the NG, graphene-coated copper meshes were wrapped around the fiber to serve as the outer electrode. Under a shear stress driven by a push action at 5 Hz, the peak output current and voltage were 2 nA and 7 mV, respectively. To fabricate the SC, a PVA/H 3 PO 4 gel electrolyte was filled in after the graphene-coated copper meshes were wrapped around the fiber. The SC showed a capacitance per unit length of 0.025 mF/cm. For the DSSC functionality, the as-grown ZnO-NWs were sensitized with a N719 dye solution, a ZnO NW-grown graphene sheet was wrapped around the fiber as the outer electrode, and finally a liquid electrolyte was poured in. The Jsc, Voc, FF, and PCE of the DSSC were 0.35 mA/cm 2, 0.17 V, 0.39, and 0.02%, respectively [32]. More of such research initiatives are required for commercial level success in this regard.

What is a photoanode made of?

The photoanode is made up of transparent conductive glass coated with transparent conductive oxide (indium- or fluorine-doped tin oxide; ITO and FTO, respectively), on which a dye-coated metal oxide semiconductor (thickness, 10–20 μm) is applied [2]. The metal oxide semiconductor layer has two functions, namely a support for the sensitizer and a carrier of photogenerated electrons from the dyes to the external circuit. The photocurrent efficiency (PCE) of DSSCs strongly depends on the dye sensitizer irradiation absorption, with the conversion efficiency of DSSCs reaching values ≤ 11% (ruthenium dye) and 13% (porphyrin dye) [5].

How does DSSC work?

The DSSC works as a photo-electrochemical cell, where the generation and transportation of electrons are caused by the combined effect of the photon energy and the chemical reactions. Although the DSSC has a bright future as a potential energy source with better integration possibilities, there are many aspects that need to be worked upon for its commercialization. One of the major challenges for DSSC is to increase the power conversion efficiency with better stability. The organic dye absorbs solar light to generate photo-excited electrons to be carried out to the external circuit through semiconductor photo-anode, and steady flow of current is obtained due to electrochemical effect. The semiconductor photo-electrode has a major role in the performance of DSSC, as recombination of the photo-generated carriers in semiconductors reduces the current that effectively decreases the power conversion efficiency of the cell. On the other hand, photo-anode should be highly transparent so that solar light reaches to the dye molecules. Historically, TiO 2 nanoparticles have been the most studied materials as DSSC photo-anode. There are also many research efforts to increase the performance of DSSC by using nanostructured and nanocomposite photo-anode to increase the charge transportation due to anisotropy in nanostructure geometry and less recombination possibility in nanocomposite materials. Carbon nanostructures have also been explored in various ways for the improvement of the PCE of DSSCs. Incorporation of CNTs in the titania (TiO 2) nanoparticle matrix significantly improved the cell efficiency. The DSSC structure fabricated with TiO 2 nanoparticles using CNT electrodes led to highly efficient cells attributed to better charge transport by CNTs [37]. The use of vertically aligned CNT forest has also increased the PCE of DSSCs by many folds [38].

What is a DSSC?

Dye-sensitized solar cell (DSSC) is another kind of solution-processed solar cells applying functional polymer component as electrode or hole transporting material. Basically, the structure of DSSC contains three parts, namely dye-sensitized photoanode, counter electrode, and redox electrolyte, which looks like a sandwich. The dye-sensitized photoanode is responsible for light absorbing and charge injection, while counter electrode is for redox pair reduction, and redox electrolyte or hole transporting material is for dye reduction. The mechanism of DSSC is depicted later. First, light travel through transparent electrode and is absorbed by dye to reach the excited state. Then the excited electrons would be injected into the conduction band of semiconductor metal oxide and transfer to external circuit. The oxidized dye would be reduced by redox pair in the electrolyte, which will be reduced by counter electrode with external circuit electrons to complete a circle. There are two grand challenges facing DSSC, as high cost platinum counter electrode and corrosive liquid electrolyte. Here the high performance counter electrode can be fabricated with conducting polymer and using a polyelectrolyte can eliminate the use of liquid electrolyte that might leak out (Saranya et al., 2015 ).

Why are carbon nanotubes used in DSSC?

Because of their 1D structure and excellent charge collecting and conducting properties , carbon nanotubes are a natural choice as an additive to the photoactive layer in conventional DSSCs, to improve electron shuttling by offering a pathway for low-resistance transport to the anode. 86–89 In a study by Kamat et al ., SWCNTs were used as an electron-shuttling scaffold for the attachment of dye-sensitized TiO 2 nanoparticles, in a conventional DSSC arrangement. 86 In assembling these cells, well-dispersed SWCNTs in organic solvent were deposited electrophoretically on to an optically transparent electrode (OTE), followed by the application of TiO 2 paste over the film and incubation in a solution of ruthenium-based dye for sensitization. Steady state emission spectrum and emission decays showed that the presence of SWCNTs did not affect the charge injection process significantly. Nevertheless, the net effects showed an increase in the IPCE of 40% compared to the cell without carbon nanotubes. However, because of the shifted Fermi level of the semiconducting layer caused by the presence of SWCNTs, the net open circuit voltage was lowered, thus resulting in no overall increase in net efficiency. 86 Multiple similar studies in which pristine 88,89 and covalently modified 87 SWCNTs were incorporated into the TiO 2 mixture before deposition showed similar increases in short circuit current because of higher conductivity and possibly better light scattering. 87 Again, the open circuit voltages tended to suffer as a result of the effect on the Fermi level of the TiO 2 layer. 87–89 As it was shown that the pristine SWCNTs did not themselves interact directly with the dye molecules, 88,89 an alternative design was presented – in which SWCNTs were first covalently bound to a ruthenium-based dye via carboxylic acid groups. 87 In this case, the open circuit voltage actually showed an increase of up to 25% with the presence of these SWCNTs; however, the short circuit density showed a negligible increase. 87 The increased open circuit voltage is attributed to a negative shift of the conduction band edge caused by chemical modification of TiO 2 from reactive moieties on the dye-functionalized SWCNTs. 87 Despite promising results, the efficiency of DSSCs incorporating SWCNTs is still well below state of the art in DSSCs. 8,18,86–89 Possible improvements in efficiency will require a high degree of effective enrichment of semiconducting species, as well as separation or doping techniques, to carefully tune the band edge potentials for optimal performance.

What are the nanostructures of DSSC?

To increase the photovoltaic properties of the DSSCs, different ZnO nanostructures, such as microspheres, nanowires, nanorods, and their nanocomposites (nanowires/nanoparticles, nanorods/nanoparticles), as well as aggregate spheres, have been applied [2]. Moreover, ordered nanostructured TiO 2 nanorods and nanotubes are of great interest for DSSC application. In recent years, the modification of the electrochemical properties of TiO 2 through doping with transition metals, such as Zr, Nb, Ta, Ni, and W, or anions, such as N and F, has been the most promising method to improve DSSC efficiency.

What is the role of a counter electrode?

The counter electrode regenerates the electrolyte, and the most commonly one comprises platinum film prepared on a glass or silicon substrate. The main role of the electrolyte is to regenerate the dye and as an electrolyte medium it should display negligible vapor pressure, low viscosity, high dielectric properties, and a high boiling point [3]. Mostly I – /I 3– inorganic solvents, inorganic ionic liquids, and solid electrolytes are employed. Among them, the iodine electrolyte is the most common and provides high DSSC efficiency.

What is a dye sensitive solar cell?

What is a Dye-Sensitized Solar Cell? Dye-sensitized solar cells (DSSC) are an efficient type of thin-film photovoltaic cell. Modern dye-sensitized solar cells, or Grätzel cells, are based on a concept invented in 1988 by Brian O'Regan and Michael Grätzel, but the concept dates back to the 1960s and 70s. DSSCs are easy to manufacture ...

What is a nanowire solar cell?

In 2004, researchers from the University of California at Santa Barbara described the performance and design of a zinc oxide nanowire-based dye-sensitized solar cell. The nanowires enable a direct electron conduction path between the conducting substrate and point of photogeneration and may offer enhanced electron transport compared to sintered nanoparticle films. The devices have a light harvesting efficiency below 10%, showing that present efficiencies and densities are enhanced by an order of magnitude by an increase in the nanowire surface area.

What materials are used in DSSCs?

Most of the materials used are low-cost, however a handful of more costly materials are necessary, such as ruthenium and platinum. There is a significant practical challenge involved in designing the liquid electrolyte for DSSCs, which must be able to remain in the liquid phase in all kinds of weather conditions.

What wavelengths are dyes sensitive to?

In 1999, newer versions were introduced with a higher frequency response that is efficient even at red and infra-red wavelengths. The dye used in these cells has a deep brown-black colour referred to as black dye, ...

How much sunlight does a dye sensitive solar panel convert to?

Presently, dye-sensitized solar panels convert about 11 – 12% of the sunlight striking them into electricity. The researchers are trying to increase the efficiency and make it comparable with silicon-based solar panels.

How is chlorophyll replaced in DSSCs?

In DSSCs, chlorophyll is replaced by a light absorbing dye, the molecules of which are excited into a higher energetic state by incoming light. This energy is collected by a structure of electrolytes and catalysts, much like the surrounding structure of a leaf in photosynthesis.

What is Will's degree?

Will has a B.Sc. in Chemistry from the University of Durham, and a M.Sc. in Green Chemistry from the University of York. Naturally, Will is our resident Chemistry expert but, a love of science and the internet makes Will the all-rounder of the team. In his spare time Will likes to play the drums, cook and brew cider.

What are dye sensitized solar cells?

Dye sensitized solar cell can be designed as indoor colorful decorative elements (see Figure 20-b). Flexible dye sensitized solar modules opens opportunities for integrating them with many portable devices, baggage, gears, or outfits (Paglia ro et al., w w w. pv- te ch.org) (see Figure 20-c and Figure 20-d). In power generation, dye sensitized modules with efficiency of 10% are attractive choice to replace the common crystalline Si-based modules. In 2010 Sony announced fabrication of modules with efficiency close to 10% and hence opportunity of commercialization of DSSC modules is attainable.

What is the operation principle of a dye sensitized solar cell?

Operation principle of the dye sensitized solar cell is explained. Some schemes used in preparation and assembly of dye sensitized solar cell are presented with few recommendations that might lead to better performance and stability of the fabricated cell.

What are the main parts of a single junction dye sensitized solar cell?

The cell is composed of four elements, namely, the transparent conducting and counter conducting electrodes, the nanostructured wide bandgap semiconducting layer, the dye molecules (sensitizer), and the electrolyte . The transparent conducting electrode and counter-electrode are coated with a thin conduc tive and transparent film such as fluorine- doped tin dioxide (SnO2). 2.1 Transparent substrate for both the conducting electrode and counter electrode Clear glass substrates are commonly used as substrate because of their relative low cost, availability and high optical transparency in the visible and near infrared regions of the electromagnetic spectrum. Conductive coating (film) in the form of thin transparent conductive oxide (TCO) is deposited on one side of the substrate. The conductive film ensures a very low electric resistance per square. Typical value of such resistance is 10-20 :

What are the three redox ions used in DSSC?

3 redox ions is used in DSSC to regenerate the oxidized dye molecules and hence completing the electric circuit by mediating electrons between the nanostructured electrode and counter electrode. NaI, LiI and R4NI (tetraalkylammonium iodide) are well known examples of mixture of iodide usually dissolved in nonprotonic solvents such as acetonitrile, propylene carbonate and propionitrile to make electrolyte. Cell performance is greatly affected by ion conductivity in the electrolyte which is directly affected by the viscosity of the solvent. Thus, solvent with lower viscosity is highly recommended. Moreover, counter cations of iodides such as Na+, Li+, and R4N+ do affect the cell performance mainly due to their adsorption on nanostructured electrode (TiO2) or ion conductivity. It has been found that addition of tert-butylpyridine to the redoxing electrolyte improves cell performance (Nazeeruddin et al., 1993) (see Figure 19). Br/Br

How many solar cells are dye sensitive?

186 Solar Cells – Dye-Sensitized Devices with that from the external load and reduced back to Iion, (Equation 6). The movement of electrons in the conduction band of the wide bandgap nanostructured semiconductor is accompanied by the diffusion of charge-compens ating cations in the electrolyte layer close to the nanoparticle surface. Therefore, generation of electric power in DSSC causes no permanent chemical change or transformation (Gratzel, 2005). S photon S o* (2) Excitation process

What is the fill factor of a solar cell?

JV FF I u u K (7) where Jsc is the short circuit current, Voc the open circuit voltage, and FF is the fill factor of the solar cell which is calculated by multiplying both the photocurrent and voltage resulti ng in maximum electric power delivered by the cell.

Is titanium dioxide toxic to solar cells?

Dye Sensitized Solar Cells - Working Principles, Cha llenges and Opportunities 177 Because it is not expensive, none toxic and having good chemical stability in solution while irradiated, Titanium dioxide has attracted great attention in many fields other than nanostructured photovoltaics such as photocat alysts, environmental purification, electronic devices, gas sensors, and photoelectrodes (Karami, 2010). The preparation procedures of TiO2film is quite simple since it is requires no vacuum facilities. Nanostructured TiO2 layers are prepared following the procedure detailed in (Hara & Arakawa, 2003; Nazerruddin et al., 1993; O' Regan & Gratzel, 1991; Smestad, 1998) “A suspension of TiO2 is prepared by adding 9 ml of nitric acid solution of PH 3- 4 (1 ml increment) to 6 g of colloidal P25 TiO2