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4 th Hybrid and Organic Photovoltaic Conference -Uppsala 2012 293 C149 - Nickel Oxide Nanostructured Electrodes for Perylenediimide-Based Dye- Sensitized Solar Cells Sebastian Feihl a , Rubén D. Costa a , Stephan Pflock a , Cordula Schmidt b , Susanne Backes b , Jörg Schönamsgruber b , Andreas Hirsch b , Dirk M. Guldi a a, Department of Chemistry and Pharmacy, Chair of Physical Chemistry I, Friedrich-Alexander-University Erlangen-Nuremberg, Egerlandstrasse 3, Erlangen, 91058, DE b, Department of Chemistry and Pharmacy, Chair of Organic Chemistry II, Friedrich-Alexander-University Erlangen-Nuremberg, Henkestrasse 42, Erlangen, 91054, DE In this work we have addressed the grand challenges associated with nickel oxide (NiO) electrodes as photocathodes in p-type dye-sensitized solar cells (p-DSSCs) and with perylenediimide (PDIs) as light harvester / electron acceptors.[1, 2] To this end, two approaches were pursued towards preparing NiO nanoparticle pastes suitable for fabricating mesoporous electrodes on conductive fluorine doped tin oxide (FTO) glass substrates. Firstly, commercially available NiO nanoparticles were dispersed in a mixture of ethanol and terpineol. Here, in order to obtain a mesoporous network two types of ethylcelluloses - EC 5 – 15 and 30 – 50 mPas - were added in a 1:1 weight ratio. After evaporating ethanol, the resulting pastes were spread on FTOs by doctor blading and tempered at different temperatures. Importantly, the influence of the calcination temperature was crucial in terms of developing efficient performing electrodes. Despite all of our efforts, the visual appearance of the resulting NiO electrodes points towards a strong heterogeneity. To circumvent this obstacle, a second approach en route towards homogenous electrodes was investigated. In that case, commercial NiO nanoparticles were mixed with a mixture of EC 5 – 15 and 30 – 50 mPas at 1:1 weight ratio and triacetin as plasticizer in ethanol. In this way, pastes containing 7 wt% of EC, 3 wt% triacetin, and different contents of NiO nanoparticles (i.e., 5 to 20 wt%) were prepared. Most importantly, the resulting electrodes showed a much improved FTO coverage, which is corroborated by scanning electron microscopy (SEM) images. In the next step, a symmetrically functionalized PDI bearing two dendrons with three carboxylate anchors each was utilized to sensitize the different NiO photoelectrodes. To interpret our results, a second, non-symmetrically functionalized PDI was used as a reference. In this particular case, one dendron is replaced by a dodeca-alkyl chain. In addition, key aspects such as the influence of chenodeoxylcholic acid (Ch-A) as a coadsorbent to prevent aggregation as well as the time dependence of the PDI uptake were keenly investigated. To conclude, devices featuring electrodes prepared with the second paste containing 10 wt% of NiO nanoparticles, baked at 400 o C, and soaked for 3 h showed the highest efficiencies for both types of PDI. The corresponding values of 0.015 and 0.016 % evolved for the symmetric and the non-symmetric PDI, respectively. References [1] Morandeira; A., et al. "Improved Photon-to-Current Conversion Efficiency with a Nanoporous p-Type NiO Electrode by the Use of a Sensitizer-Acceptor Dyad". J. Phys. Chem. C 112, 1721-1728 (2008 [2] Le Pleux, L.; et al. "Synthesis, photophysical and photovoltaic investigations of aceptor-functionalized perylene monoimide dyes for nickel oxide p-type dye-sensitized solar cells". Energy Environ. Sci. 4, 2075-2084 (2011). © SEFIN 2012
4 th Hybrid and Organic Photovoltaic Conference -Uppsala 2012 294 C150 - A platinum-based poly(aryleneethynylene) containing thiazolothiazole group with high hole mobility for organic photovoltaic and field-effect transistor applications Lei Yan, Xiaohui Wang, Xingzhu Wang, Xun Chen Xiangtan University, Key Laboratory of Low Dimensional Materials and Application Technology of Ministry of Education and College of Chemistry, Xiangtan University, Xiangtan,411105, CN Harvesting energy directly from the sun is one of the most important methods to address the world energy need. Polymer solar cells (PSCs) have attracted a lot of attention in recent years due to their potential use for the new generation renewable energy sources. 1 They have many advantages over the silicon-based devices such as low cost, light weight, flexibility, an easy printing of polymer on the substrate, and easy manufacture of the devices. Recently, some devices made with conjugated polymers have shown a power conversion efficiency (PCE) approaching ~8% when blended with fullerene derivatives (such as PC61BM and PC71BM). 2 Despite considerable progress in this field, the PCE of PSCs must be further improved for commercialization. The decisive parameters that determine the efficiency of PSCs are the open-circuit voltage (Voc), short-circuit current (Jsc), and fill factor (FF). Voc is limited by the difference between the highest occupied molecular orbital (HOMO) of the donor and the lowest unoccupied molecular orbital (LUMO) of the acceptor. Figure 1 Absorbance spectrum of the [Ru(4,4'-dicarboxy-2,2'-piridine)2(benzotriazole)2](PF6) and two successive deprotonation products (a) and photoaction spectrum compared with the N719 dye (b). However, the Jsc and FF are directly limited by the charge carrier mobility. Higher charge carrier mobilities enable better carrier transport within an active layer without significant photocurrent loss due to the recombination of opposite charges. High charge carrier mobilities also lead to high fill factors. Thiazolothiazole has a rigid and coplanar fused ring, and thereby ensures highly extended π-electron system and strong π-stacking. As a result, conjugated small molecules and polymers based on electron-poor thiazolothiazole exhibited high charge carrier mobilities. We and others have recently demonstrated efficient solar cells based on polyplatinyne:PCBM bulk heterojunctions with high photovoltaic performance. 3 Here, we report the application of a new soluble, solution-processable metallopolyyne of platinum(II) functionalized with electron-deficient thiazolothiazole spacer in bulk heterojunction solar cells and organic field-effect transistors (OFETs). The new copolymer semiconductor indeed exhibited an impressive field-effect carrier mobility of up to 2.0 x10 –2 cm 2 · V –1 · s –1 , and bulk heterojunction solar cells made from P produced a power conversion efficiency of 2.16% under 100 mW cm –2 AM 1.5 G irradiation in ambient air. © SEFIN 2012
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