Photovoltaics thiophene-based materials

In Chapter 3, Peter Skabara reviews the emerging subclass of thiophene-based materials, fused oligoth-iophenes. Special attention to this subclass of oligothiophenes is well justified by, among other reasons, the very high stability of a thienothiophene building block, which makes it popular for applications in thin-film transistors and photovoltaics. 

Photovoltaic devices based on pure 29 and 29 PCBM blend as the active layer is fabricated. It was interesting to observe that a device with pure 29 showed a higher power conversion efficiency (0.05%) compared to that consisting of a 29/PCBM blend (0.0.0024% to 0.041%). The good performance in the photovoltaic cells with 29 only was attributed to the efficient charge separation process and that the material exhibits efficient hole and electron transport. The C6o moieties facilitated that electron transport, while the holes are transported via the hopping between Pt2-thiophene units. 

During the last decade, there have been countless studies devoted to the synthesis of different thiophene-based polymers and oligomers for photovoltaic applications and various photoconversion efficiencies ranging from 0.1 to 5 % have been reported for devices based on such materials. We have chosen some references that cover a small part of the literature on polythiophene-based [40-54] and oligothiophene-based [55-60] devices with relatively successful photovoltaic performance. Figure 18.3 shows the molecular structures of some of the most successful materials, and their optical bandgaps and PCE are given in Table 18.1. 

LEE 11] Lee S.-M., Lee S.-B., Kim K.-H. et al., Syntheses and photovoltaic properties of polymeric sensitizers using thiophene-based copolymer derivatives for dye-sensitized solar cells . Solar Energy Materials and Solar Cells, vol. 95, no. l,pp. 306-309,2011. 

Finally, conjugated materials 40 based on poly(phenylene thiophene) and poly (fluorene thiophene) main chain polymers functionalized with pendant trithiocyanato ruthenium terpyridine complexes were synthesized by the Suzuki coupling reaction. Heterojunction photovoltaic cells with the simple structure ITO/polymer/C-60/Al were fabricated. Under simulated AM1.5 solar light illumination, the short circuit currents, open circuit voltages, and power conversion efficiencies of the photovoltaic cells were measured to be 1.53-2.58 mAcm 2, 0.12-0.24 V, and 0.084-0.12%, respectively [77]. 

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