Efficiency of a solar cell

The diffusion length of photogenerated charge carriers is one of the important parameters governing the efficiency of a solar cell. In conventional cells, this is an intrinsic property of the semiconductor and its purity [34]. However, in DSSCs, the diffusion length is a function of the rate of reaction (4) and, thus, varies with different redox couples, surface treatments, and so forth. When the oxidation of R [reaction (2)] is chemically irreversible, the diffusion length of electrons is effectively infinite, whereas with kinetically fast, reversible redox couples (see Section VI), it approaches zero with unpassivated interfaces. 

This equation shows that the efficiency of a solar cell of this type is controlled by many factors and not only by light absorption by dye. 

When we attempt to establish a relationship between cell performance and TCO, it is indispensable to break down the conversion efficiency of a solar cell... 

The efficiency of a solar cell is strongly dependent on conditions such as cell temperature, and incident light intensity and spectral content. Standard reporting conditions (SRC) have therefore been defined so that the performance of a solar cell can be quantified in a reproducible way. The standard reporting conditions are specified as ... 

Furthermore, the production is expected to be easily scalable. This technology is currently developed by many researchers around the world, but has not yet reached the marketplace. In order for polymer solar cells to become economic their efficiency must be improved. The power conversion efficiency of a solar cell is dictated by three factors (i) the fraction of sunlight that can be absorbed, (ii) the fraction of absorbed photons that lead to extracted charges ( internal quantum efficiency ), and (iii) the energy that is retained by the extracted charges (ideally close to the open-circuit voltage ). In this review we will refer often to factors (ii) and (ui). Their interplay is not well understood and at present these have not both been optimized simultaneously even in state-of-the-art organic solar cells. 

When the temperature of a solar cell rises, cell conversion efficiency decreases because the additional thermal energy increases the thermally generated minority (dark-drift) current. This increase in dark-drift current is balanced in the cell by lowering the built-in barrier potential, lU, to boost the majority diffusion current. The drop in F causes a decrease in and F. Therefore, a cell s output, ie, the product of F and decreases with increasing cell temperature. is less sensitive to temperature changes than F and actually increases with temperature. 

SN)X can act as an efficient barrier electrode in ZnS junctions, increasing the quantum efficiency of the blue emission by a factor of 100 over gold.14 It can also be used to increase the efficiency of GaAs solar cells by up to 35%. Metal ions interact more strongly with a poly(sulfur nitride) surface than with other metal electrodes. This property has stimulated investigations of possible applications of (SN)X as an electrode material. 

A. De Vos, Detailed balance limit of the efficiency of tandem solar cells,... 

A. Luque, A. Marti, Increasing the efficiency of ideal solar cells by photon induced transitions at intermediate levels, Phys. Rev. Lett. 78 (1997) 5014-5017. 

Fig. 16 Photocurrent-voltage curve of a solar cell based on complex 26. The cell was equipped with an anti-reflective coating. The conversion efficiency in full AM 1.5 sunlight illumination (100 mW cm-2) is 11.18%. The cell is masked with black plastic to avoid the diffusive light leaving an active cell area of 0.158 cm2...

The overall efficiency r/eff of a solar cell is calculated from... 

Siemens researchers achieve a breakthrough in increasing the efficiency of organic solar cells, News release for the Trade Press by Siemens, Munich, 7 January 2004. C E Printed plastic solar cells. 

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