Organic polymeric solar cells

Also, the chemistry and polymerization of discotic monomers has been reviewed [10]. Their current and emerging uses are in optical compensation films for liquid crystal displays, carbon nanostructures, organic electronics, solar cells, light-emitting diodes, and field-effect transistors. 

Recently, a new method for the preparation of active layers of polymeric solar cells without the need for thermal post-treatment to obtain optimal performance was presented by Berson et al. [263]. P3HT nanofibers were obtained in highly concentrated solutions, which enabled the fabrication of nanostructured films on various substrates. By mixing the nanofibers with a molecular acceptor such as PCBM in solution, it was possible to obtain in a simple process a highly efficient active layer for organic solar cells with a demonstrated PCE of up to 3.6%, which was achieved with an optimum composition of 75 wt% nanofibers and 25 wt% P3HT. 

C. H. Duan, C. M. Zhong, F. Huang and Y. Cao, Interface Engineering for High Performance Bulk-Heterojunction Polymeric Solar Cells, in Organic Solar Cells Materials and Device Physics, ed. W.C.H. Choy, Springer, 2013, pp. 43-79. 

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. 

If we compare the data in Table 8.5 with the barrier requirements set in polymer electronics (Fig. 8.11), it is evident they cannot be met with metallized films, not even with ultra-high-barrier films, multi-layer structures from metal evaporation, and polymeric layers. For transparent barriers, as required for OLEDs, displays, organic solar cells, etc., evaporated oxide layers are even further from meeting the values required. 

H. Spanggaard, F.C. Krebs, A brief history of the development of organic and polymeric photovoltaics, Solar Energy Materials and Solar Cells 83 (2004) 125-146. 

To help the design of optimized polymeric materials for BHJ solar cells, several models have been recently proposed [87-89]. The combination of these models and DFT calculations has recently led to the synthesis of several other poly(2,7-carbazole) derivatives (P17, P19-P22). Symmetric polymers (P17-P19) show better structural organization than asymmetric polymers (P20-P22), resulting in higher hole mobilities and power conversion efficiencies. Moreover, their low HOMO energy levels (ca. (- 5.6)—(— 5.4)eV) provide an excellent air stability and relatively high Voc values (between 0.71-0.96 V). 

Certain organic materials also possess semiconductor properties and can be employed in PV cells, a fact that has recently been attracting growing interest since the advent of novel polymeric materials [22, 60-66]. Table 6.5 lists some typical polymers used in solar cells. 

A., Nazeeruddin, M.K., Gratzel, M., Seok, S.I., 2013. Efficient inorganic-organic hybrid heterojunction solar cells containing perovskite compound and polymeric hole conductors. Nat. Photon. 7,486-491. 

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