Organic solar cells systems

The aim of this chapter is to give a state-of-the-art report on the plastic solar cells based on conjugated polymers. Results from other organic solar cells like pristine fullerene cells [7, 8], dye-sensitized liquid electrolyte [9], or solid state polymer electrolyte cells [10], pure dye cells [11, 12], or small molecule cells [13], mostly based on heterojunctions between phthaocyanines and perylenes [14], will not be discussed. Extensive literature exists on the fabrication of solar cells based on small molecular dyes with donor-acceptor systems (see for example [2, 3] and references therein). 

It is the purpose of this chapter to introduce photoinduced charge transfer phenomena in bulk heterojunction composites, i.e., blends of conjugated polymers and fullerenes. Phenomena found in other organic solar cells such as pristine fullerene cells [11,12], dye sensitised liquid electrolyte [13] or solid state polymer electrolyte cells [14], pure dye cells [15,16] or small molecule cells [17], mostly based on heterojunctions between phthalocyanines and perylenes [18] or other bilayer systems will not be discussed here, but in the corresponding chapters of this book. 

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... 

Organic solar cell based on fullerene modified by heterocycles, porphyrin systems, and polymers with heterocyclic fragments 04MI53. 

Abstract In solar applications microstructured polymer surfaces can be used as optically functional devices. Examples are antireflective surfaces, dayUghting, sun protection systems, concentrator photovoltaic modules and light trapping structures in organic solar cells. The examples and the principles of function of the respective microstmctures are described in detail. The suitability of different manufacturing methods is discussed. Two of them, ultraprecision machining and interference lithography are described. For the latter experimental results are shown. Finally, the opportunities and the risks of the shown approaches are discussed. 

All organic systems are characterised by a high absorption coefficient at the maximum of the absorphon spectrum, it is of the order of 10 cm (cf Chap. 6). Organic solar cells therefore contain layers whose thickness is less than the wavelength of light. Making use of multiple reflections, e.g. at mirrored interfaces, the layer thicknesses can be reduced to well under 100 nm. This is another differ-... 

In the next subsections, we will describe organic solar cells, their physical fundamentals and typical experimental results, using as an example the system CuPc/Cgo (Fig. 11.15). 

Whether organic solar cells will be commercially employed in the future will be decided by economic aspects. It is certain, however, that their fabrication is simpler and cheaper than that of silicon-based solar cells. Furthermore, they have the advantage that they can be produced on flexible and light substrates. In addition, solar cells based on polymer systems can be fabricated using printing technology. 

Much effort has been devoted to applying electron transfer in H-bonding system for the construction of optoelectronic devices and organic solar cells. For example, fullerene derivative and perylene bisimide have been assembled to form a El-bonded supramolecular system 28 through triple amino-carboxyhc acid interaction [86]. Under 63.2 mW/cm white light irradiation, the film made from the assembly on indium tin oxide (ITO) electrodes generated a steady and rapid photocurrent. The response of on/oflf cycling was prompt and reproducible. 

T. Kawatsu, V. Coropceanu, A.J. Ye, and J.L. Bredas, Quantum-chemical approach to electronic coupling Application to charge separation and charge recombination pathways in a model molecular donor-acceptor system for organic solar cells, J. Phys. Chem. C, 112, 3429-3433 (2008). 

Semiconductors and Semimetals. Vol. 85. Quantum EfiBciency in Complex Systems. Part II. From Molecular Aggregates to Organic Solar Cells. U. Wurfel, M. Thowart, and E. Weber (Eds.). Elsevier, Chapter 9, pp. 312, 341 (2011). 

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