Polymeric solar cells

The best performing solar cell fabricated from these compounds exhibited a power conversion efficiency of 9.14%, which demonstrates the great potential of asymmetric indenothiophene for high 

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Landi BJ, Castro SL, Ruf HJ, Evans CM, Bailey SG, Raffaelle RP (2005). CdSe quantum dot-single wall carbon nanotube complexes for polymeric solar cells. Solar Energy Mater And Solar Cells 87 733-746. 

Schubert M, Yin CH, Castellani M, Bange S, Tam TL, Sellinger A, Horhold HH, Kietzke T, Neher D (2009) Heterojunction topology versus fill factor correlations in novel hybrid small-molecular/polymeric solar cells. J Chem Phys 130 094703... 

In the following, we discuss strategies for optimizing the power efficiency of polymeric solar cells based upon bulk heterojunctions. 

Polymeric solar cells with a bandgap > 2 eV are spectrally so badly mismatched to the solar spectrum that their efficiency is severely restricted. It is essential to develop polymeric semiconductors with lower bandgap. Low bandgap polymeric semiconductors behave similarly in conjunction with fullerenes as n-type semiconductors (acceptors). 

The portion of the solar light that typical polymeric solar cells absorb is limited. In Fig. 2a the absorption coefficients of thin films from two common conjugated polymers and PCBM are shown in comparison to the AM 1.5 solar... 

Polymeric solar cell with oriented and strong transparent carbon nanotube anode. Phys Status Solidi B 243 3528... 

In order to uncover the photophysical processes and the loss mechanism in polymeric solar cells, two main approaches can be distinguished electrical measurements and time-resolved optical spectroscopy. Electrical measurements have the fundamental disadvantage that they lack time and spatial resolution to probe the processes that occur directly after exciton ionization. To investigate these dynamics, time-resolved spectroscopy is a much more promising approach, because ultrafast laser systems allow observing these proeesses directly with subpicosecond time resolution. 

An advancement in efficiency of polymeric solar cells, from 3 to 5%, came in 2009 when it was observed that promising efficient charge transfer materials can be prepared from combinations of poly (alkyl-thiophenes) donors with l-(3-methoxycarbonyl)propyl-lphenyl-[6,6]-methanofullere acceptors [265]. Mild heating disperses the acceptor molecules among the donor molecules ... 

Other applications in micro and nanoelectronics are been developed with the help of CNTs. One example is the development of sensors that are placed in situ in concrete for the evaluation of internal porosity [13], through the use of oriented nanotube membranes that vibrate when they are in the middle. For certain applications, the solution to this approach is the synthesis of films of aligned CNTs [14-17], enabling the manufacture of monitors and microwave generators. This is possible because of their ability to emit electron by field effect [18]. The applications of these films also include the development of polymeric solar cells the semiconducting properties of CNTs films with anisotropic morphology result in a route for the separation of pairs and conduction electrons/holes generated by photons [19]. 

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. 

Figure 13.2 (a) Estimation of the material costs of polymeric solar cells (b) estimated costs of polymeric solar cells. Reproduced from ref. 5 with the permission of RSC Publications, 2014. 

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