Literature Review on Dye Sensitized Solar Cells (DSSC)

 Literature Review on Dye Sensitized Solar Cells (DSSC)
Literature Review
1. Historical Background
The historical backdrop of the sensitivity of materials such as semiconductors to bandwidth of light greater than that relating to the band – gap has been shown somewhere else. It is an intriguing union of photo electrochemistry and photosensitivity, in which both of them depend on photo sensitive affected by separation of electrons or charges at a interface of liquid – solid. (Grätzel, 2003) The silver halides utilized as a part of photosensitivity possess band gaps of the magnitude in the range of 2.7 to 3.2 eV, and are along these lines not sensitive to a significant part of the natural light (visible light), generally as it stands the TiO2 now utilized as a part of the photo – electrochemical gadgets. The principal panchromatic film, ready to render the picture of a scene reasonably into highly contrasting, took place after the work of Vogel in Berlin after 1873, in which he related dyes with the halide semiconductor grains. (Grätzel, 2003) The main sensitization associated with the photo – electrode took after presently, utilizing chemistry in its production. Although, the realization of the parallelism between the two techniques, a recognition that the same dyes on a basic level can work in both and confirmation that their working process is basically done by the infusion of electrons that are acquired from photo – energized dye molecules inside the conduction type of band that is made up of n-type semiconductor substrates. In ensuing years the thought created that the dye can work most effectively if it is chemisorbed on the semiconductor surface. (Grätzel, 2003)

Titanium dioxide was the semiconductor that was utilized for this purpose. The chosen material has numerous preferences for sensitized photochemistry also, photograph electrochemistry: it is broadly accessible, cheaper, biocompatible material, non-dangerous and hence is even utilized as a part of health care products and domestic applications. The standard dye at the time was tris (2,2´-bipyridyl-4,4´-carboxylate) ruthenium (II), the carboxylate capacity being the connection developed by the process of chemisorption to the oxide substrate. (Grätzel, 2003) Advance from that point, until the declaration in the year 1991 of the sensitized electro – chemical type of photovoltaic gadget with a change effectiveness around then of 7.1 percent under sun oriented brightening. That development has preceded dynamically from that point forward, with confirmed proficiency now more than 10%. (Grätzel, 2003)

2. Introduction to DSSC
Sunlight is one of the naturally and abundantly available sources of energy and researchers have been working from several decades to make maximum use of the sunlight to harness energy. Several innovations made in this regard involve energy storage, solar water heater and atomic waste degradation etc. One such innovation involve the use of sunlight is to generate electricity which is possible by storing the sunlight energy in batteries. (Kalyanasundaram and Grätzel, 2009) Until now, the photovoltaic technologies that are implemented commercially are basically dependent on inorganic materials that have disadvantages of high production costs and also preparation methods are high energy consuming methods. It was also noted that, materials such as CdTe are not available abundantly in nature and also are toxic in nature. Thus, the solution available to solve this issue is to make use of organic photovoltaic methods. But according to researchers, who conducted their study purely on organic photovoltaic said that the efficiency of operation of organic photovoltaic are much lesser than the efficiency obtained from the inorganic – based photovoltaic technologies. (Nazeeruddin, Baranoff and Grätzel, 2011)

Photo electrochemical solar based cell is by and large made out of a photoactive type of semiconductor material consisting of a working anode and a cathode and is either made up of semiconductors or metals such as Pt. Both cathodes are inundated in the solution of electrolyte which consists of appropriate redox mix. In the event that the semiconductor – electrolyte interface (SEI) is ignited with a light wave having energy more prominent than the semiconductor’s band – gap, photo – generated electrons / openings are isolated. (Robertson, 2006) The photo – generated minority transporters, settle down at the interface of semiconductor – electrolyte effectively. Photo – generated minority carrier transporters aggregate at the posterior position of semiconductor material. Taking the assistance of a charge – gathering substrate, photo – generated greater part bearers are transported by means of a heap to the cathode where these bearers respond electrochemically with the electrolyte solution of redox. (Robertson, 2006) A spearheading photo electrochemical investigation was acknowledged by getting photocurrent among two different catho