Parallel-module

A simple fabrication procedure of making DSSC modules is parallel connection. According to this structure small cells in the form of long stripes are connected in parallel.

Fig. 8. (a) W-Module (b) Z-Module DSSC (Seo et al., 2009)

In this structure parallel grids utilizing conductive fingers to collect current are printed on the two electrodes of the cells. The printing method of current collectors is quite similar to that applied in conventional photovoltaics based on silicon. Common metals used as current collectors reducing the distance of electron transfer and internal resistance of FTO glass are: Ag, Cu, Ni, Ti. The solar cell efficiency is considerably reduced when it is converted to module despite the high unit cell efficiency. This is because of the increased possibility to lose electrons, which are created by light absorption, through either internal defect or recombination with hole at interface with other materials during the delivery when the electrode area to absorb light enlarges. Therefore, the efficiency radically decreases when DSSC active electrode width becomes greater than 1 cm (Wang et al., 2010).

Pt

metal Fingers ——— polymer

Electrolyte filling

Fig. 9. Parallel connection of DSSC in a module

It is essential to design and manufacture effective packaging system along with designing photovoltaic absorption-use electrode and charge collection-use grid in order to allow the electron flow to collect without losses in large-areas like module. Mainly opposed cell module has been manufactured and researched since 1995 until now. The opposed cell module used ceramic fragment paste (glaze) or polymer in order to protect the conductive internal pattern from electrolytes. Such opposed cell R&D activities slowed down until 2001 and newly begun afterwards (Displaybank, 2010). The parallel type module records broad active area and high conversion efficiency. Large-area photoelectric chemical solar cell must use transparent electrode which has weaker electric conductivity than the metal wiring that it requires a grid to play a role of charge collection to realize smooth electron delivery. Therefore, the large-area solar cell exhibits different carrier generation and delivery from the unit cell.

A general grid in DSSCs mainly uses metal material. This is connected to active area decrease and becomes the factor to increase the generation unit cost of cell. Therefore, it is essential to secure effective module design and manufacturing technology for commercialization.

The DSSC is manufactured by a process that is relatively simpler than the conventional solar cells made of silicon and compound semiconductor solar cells, but it entails a shortcoming to generate metal corrosion when using the metal with outstanding electric conductivity as grid due to iodine based electrolyte. Therefore, the DSSC is in need for electrolyte development with outstanding activity without corrosive property or metal development with outstanding electric conductivity without being separated or corroded from the electrolyte. The inverter development must progress to be appropriate for DSSC which secures electric property that is different from the conventional silicon based solar cell.

In order to accomplish this, a circuit must be composed to match arrangement and response properties of DSSC module. The inverter technology development maximizes the DSSC power generation efficiency. The system is matched to the solar cell’s generation property in order to effectively supply the power of electric condenser, which stores electricity generated during daytime, at desirable time. The commercialization of DSSC requires power system development together with unit cell efficiency enhancement technology development. The DSSC commercialization is delayed due to unprepared peripheral technologies despite the fact that its current power generation unit cost can realize commercialization (Displaybank, 2010). Right now, the ultra small high efficiency inverter technology is insufficient for module/system efficiency enhancement and manufacturing technology of module which can be installed in targets such as buildings.

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