Gratzel cells DSSCs

The new DSSC developed by Gratzel and co-workers, the so-called Gratzel cell, has very attractive characteristics as follows ... 

Figure 15.6 shows the relationship between Jsc of the Gratzel cell and the viscosity of various liquid media under the same conditions [21]. The Jsc of the DSSC system depends simply on the viscosity of the liquid media. However, as described above, the Jsc of iodide-based RTILs is much higher even where viscosity is higher than 200 mPas at 25°C. As shown in the figure, the amount of iodine (I2) affects the improvement in Jsc- This implies that the diffusion coefficient of the iodide... 

Closely related to liquid electrolyte dye-sensitized solar cells (DSSCs, also known as Gratzel cells ) [283,284], the class of soHd-state DSSCs has been developed to improve device stability and reduce complications in the production process [285-288]. Thus, although polymers can be utilized as replacements for sensitizing dyes (as in liquid electrolyte DSSCs) [289-291], the main effort in applying conjugated polymers focuses on soHd-state DSSCs [45,292-298]. With environmentally friendly production of this polymer based solid-state DSSC in mind, a device based on water-soluble polythiophene derivative has been presented as well [299]. 

In 1991, the Gratzel group reported the first dye-sensitized solar cell (DSSC), which was based on the photosensitization of dye adsorbed onto nanocrystalline Ti02 films [62]. Since then, as a promising renewable photovoltaic technology, DSSCs have... 

A reverse PET, namely photoinduced charge injection from an electronically excited chromophore to a semiconductor surface, is typically the initial step in dye-sensitized solar cells (DSSCs) of the Gratzel-type, for example, with a trinuclear ruthenium dye 51 (Figure 20.11a) [69]. Such a PET step, reminiscent of the charge separation in DSSCs or in PS II, has been visualized by Kelvin probe force microscopy on a donor-chromophore-acceptor nanocomposite poly[TPA-Ru (tpy)2] ZnO (tpy, 2,2 6, 2"-terpyridine) 52 prepared from a ZnO-immobilized [Ru (tpy)2] chromophore (Figure 20.11b, TPA, tripheny-lamine) [70]. In 52, both the electron acceptor (ZnO) and the electron donor (TPA) are assembled in a directional manner to assist the charge separation step... 

Papageorgiou et al. reported the first example of an RTIL-based dye-sensitized solar cell system (Gratzel ceU). They found that l-hexyl-3-methylimidazolium iodide, denoted as HMI-I, melts at room temperature [8]. However, the viscosity of HMI-I is very high, at over 1000 mPas at room temperature. Therefore the /sc of DSSC when HMI-I is used (0.75 mA cm at the irradiation of 120,000 Lux [= 1 sun]) is much lower than that when an organic solvent is used (over 15 mA cm at 1 sun). This indicates that the slow diffusion of the iodide/triiodide redox... 

In the seminal Nature paper of 1991, O Regan and Gratzel reported an order-of-magnitude increase for DSSC type solar cell efficiency to 7-8%. ° With regards to stability, a turnover number of 5 x 10 was measured for the sensitiser (a trimeric ruthenium complex).This was followed up by the introduction of the ruthenium bipyridyl-based N3 dye (Figure 3.15), giving efficiencies around 10%. 

In 1996, Kay and Gratzel introduced the concept of monolithic DSSCs, where the device is assembled on one substrate rather than two in the sandwich cell. The assembly process and the device structure is shown in Figure 3.76. 

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