Solar cells organic, types

As a class of n-type organic semiconductors, PBI derivatives have received considerable attention for a variety of applications [312, 313], for example, for organic or polymer light-emitting diodes (OLEDs and PLEDs) [314, 315], thin-film organic field-effect transistors (OFETs) [316, 317], solar cells [318, 319], and liquid crystals [320]. They are also interesting candidates for single-molecule device applications, such as sensors [321], molecular wires [322], or transistors [141]. 

Fig. 17.5 Scheme of basic processes occurring in DSSCs (a) and organic solar cells (c). (b) Band bending for an n-type semiconductor and a p-type semiconductor in equilibrium with an electrolyte. 

Liu Z, He D, Wang Y et al (2010) Solution-processable functionalized graphene in donor/ acceptor-type organic photovoltaic cells. Solar Energy Mater Solar Cells 94 1196-1200... 

Many dyes are decolorized and ultimately mineralized by photocatalysis. In the degradation of azo dye,18 21) the degradation rate decreases in the order monoazo > diazo > triazo.1819) Three processes including oxidation and reduction are considered to occur simultaneously in the photocatalytic degradation of dye. These are illustrated in Fig. 9.9. Process 1 is the common photocatalytic degradation process of organic compounds. Process 2 is spectral sensitization as observed in a wet-type solar cell. In process 3 one moiety of dye molecule serves as the electron acceptor, suppressing recombination between electron and positive hole. 

Quasi-solid state dye-sensitized solar cells (DSCs) have been constructed using a new polymeric ionic fluid as the electrolyte.119 The electrolyte was synthesized by the sol-gel route using MTMSPI+I as the precursor that was made by derivatizing methylimidazolium with triethyoxysilane. Condensation of this material in the presence of formic acid and in the absence of water led to Si-O-Si-O-type polymerization and formation of a polysilsesquioxane-type structure. When this material was mixed with iodine, it served as a redox electrolyte for DSCs. The DSCs made this way are robust and easy to assemble but their efficiency of 3.1% is relatively low. However, possible improvement lies in modification of the organic groups attached to the polysilsesquioxane backbone. 

Research on the solid state dye-sensitized solar cells (DSC) has gained considerable momentum recently as this embodiment is attractive for realizing flexible photovoltaic cells in a roll-to-roll production. The spzro-OMeTAD has been the most successful p-type organic conductor (hole transport material) employed. Its work function is about 4.9 eV and the hole mobility 2 x 10-4 cm2 s x. A schematic diagram of the solid sate DSC with the structure of this hole conductor is shown in Fig. 19. Reported first in 1998, the con-... 

Liu prepared a sandwich type coordination compound (103) from porphyrin and phthalocyanine with the assistance of a microwave. The resulted compounds showed good solubility in conventional organic solvents. The photoelectric conversion properties have been tested with a Gratzel type cell. The results revealed that the sandwich type compound showed better photo-electric conversion efficiency than the corresponding monomeric porphyrin or phthalocyanine precursors. The short-circuit photocurrent of the solar cell with this sandwich type compound as sensitizer, was, as high as 691.31 A cm-2, which was much better, than those of porphyrin or phthalocyanine monomers [100]. 

The solar energy world finds itself on the horns of a dilemma, having to choose between metal-based solar cells, which perform well but are costly, and organic solar cells, which are cheap but inefficient. One answer is to combine the two types of semiconductor to produce a hy-... 

Possible applications of ZnO nanostructures are UV lasers (up to now only with optical excitation) [84], chemical sensors [85], or transparent substrates for thin film solar cells, e.g. as an alternative to Ti02 in injection type solar cells or in organic solar cells [79,86,87]. In the latter two applications the increased effective surface of arrays of ZnO nanowires leads to... 

Furthermore, these data strongly suggest that the positive temperature dependence of Isc, FF, and r) may be characteristic for solar cells based on organic semiconductors that show a temperature-activated behavior for charge transport, resulting in higher mobility/conductivity at higher temperatures (as also observed, for example, for some types of amorphous silicon solar cells [162]). 

---