Suchergebnisse

Homocoupling of monomers in a palladium-catalyzed copolymerization of donor-acceptor polymers affects the perfect alternating structure and may deteriorate the performance of such materials in solar cells. Here we investigate the effect of homocoupling bis(trialkylstannyl)-thiophene and -bithiophene monomers in two low band gap poly(diketopyrrolopyrrole-alt-oligothiophene) polymers by deliberately introducing extended oligothiophene defects in a controlled fashion. We find that extension of the oligothiophene by one or two thiophenes and creating defects up to at least 10% does not significantly affect the opto-electronic properties of the polymers or their photovoltaic performance as electron donor in solar cells in combination with [6,6]-phenyl C-71 butytic acid methyl ester as acceptor. By using model reactions, we further demonstrate that for the optimized synthetic protocol and palladium-catalyst system the naturally occurring defect concentration in the polymers is expected to be less than 0.5%. ; We thank Dr Koen Hendriks for valuable discussions. G. H. L. Heintges acknowledges the Agency for Innovation by Science and Technology in Flanders (IWT). This project has further received funding from the European Research Council under the European Union's Seventh Framework Programme (FP/2007-2013)/ERC Grant Agreement No. 339031 and from the Ministry of Education, Culture and Science (Gravity program 024.001.035).

The characteristic doping process in polymer light-emitting electrochemical cells (LECs) causes a tradeoff between luminescence intensity and efficiency. Experiments and numerical modeling on thin film polymer LECs show that, on the one hand, carrier injection and transport benefit from electrochemical doping, leading to increased electron-hole recombination. On the other hand, the radiative recombination efficiency is reduced by exciton quenching by polarons involved in the doping. Consequently, the quasi-steady-state luminescent efficiency decreases with increasing ion concentration. The transient of the luminescent efficiency shows a characteristic roll-off while the current continuously increases, attributed to ongoing electrochemical doping and the associated exciton quenching. Both effects can be modeled by exciton polaron-quenching via diffusion-assisted Forster resonance energy transfer. These results indicate that the tradeoff between efficiency and intensity is fundamental, suggesting that the application realm of future LECs should be sought in high-brightness, low-production cost devices, rather than in high-efficiency devices. ; Funding Agencies|NanoNextNL, a micro and nanotechnology consortium of the Government of the Netherlands; [NNNL.06D.04]

By analyzing the optical band gap and energy levels of seven different regioregular terpolymers in which two different electron-rich donor moieties are alternating with a common electron-deficient acceptor unit along the backbone, we establish a direct correlation with the properties of the corresponding binary copolymers in which one donor and one acceptor are combined. For this study, we use diketopyrrolopyrrole as the common acceptor and different pi-conjugated aromatic oligomers as donors. We find that the optical band gap and frontier orbital energies of the terpolymers are the arithmetic average of those of the parent copolymers with remarkable accuracy. The same relationship is also found for the opencircuit voltage of the bulk heterojunction solar cells made with the ter- and copolymers in combination with [6,6]-phenyl-C-71-butyric acid methyl ester. Comparison of these findings with data in the literature suggests that this is a universal rule that can be used as a tool when designing new pi-conjugated polymers. The experimental results are supported by a semiempirical quantum chemical model that accurately describes the energy levels of the terpolymers after parametrization on the energy levels of the copolymers and also provides a theoretical explanation for the observed arithmetic relations. ; G.H.L.H. acknowledges the Agency for Innovation by Science and Technology in Flanders (IWT). A.B. acknowledges Fonds de recherche du Quebec - ́ Nature et technologies (Grant 173542).The work was further supported by the European Research Council under the European Union's Seventh Framework Programme (FP/2007-2013) (ERC Grant Agreement No. 339031), the Ministry of Education, Culture and Science (Gravity program 024.001.035), and the NWO Spinoza prize awarded to R.A.J.J. by The Netherlands Organization for Scientific Research (NWO). ; Meskers, SCJ; Janssen, RAJ (reprint author), Eindhoven Univ Technol, Mol Mat & Nanosyst, NL-5600 MB Eindhoven, Netherlands; Eindhoven Univ Technol, Inst Complex Mol Syst, NL-5600 MB Eindhoven, Netherlands; Dutch Inst Fundamental Energy Res, NL-5612 AJ Eindhoven, Netherlands. s.c.j.meskers@tue.nl; r.a.j.janssen@tue.nl

The effect of gradually replacing the branched alkyl side chains of a diketopyrrolopyrrole (DPP) conjugated polymer by linear side chains containing branched siloxane end groups on the photovoltaic performance of blends of these polymers with a common fullerene acceptor is investigated. With an increasing proportion of siloxane side chains, the molecular weight and solubility of the polymers decreases. While the siloxane containing polymers exhibit a higher hole mobility in field-effect transistors, their performance in solar cells is less than the polymer with only alkyl sides chains. Using grazing-incidence wide-angle X-ray scattering, transmission electron microscopy, and fluorescence spectroscopy we identify two main reasons for the reduced performance of siloxane containing polymers in solar cells. The first one is a somewhat coarser phase-separated morphology with slightly wider polymer fibers. This is unexpected as often the fiber width is inversely correlated with polymer solubility. The second one is stronger non-radiative decay of the pristine polymers containing siloxane side chains. ; G. H. L. Heintges acknowledges the Agency for Innovation by Science and Technology in Flanders (IWT). This project has further received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No. 747422, from the European Research Council under the European Union's Seventh Framework Programme (FP/2007-2013)/ERC Grant Agreement No. 339031 and from the Ministry of Education, Culture and Science (Gravity program 024.001.035).

Polymorphism of organic semiconducting materials exerts critical effects on their physical properties such as optical absorption, emission and electrical conductivity, and provides an excellent platform for investigating structure-property relations. It is, however, challenging to efficiently tune the polymorphism of conjugated polymers in aggregated, semi-crystalline phases due to their conformational freedom and anisotropic nature. Here, two distinctly different semi-crystalline polymorphs (beta(1) and beta(2)) of a low-bandgap diketopyrrolopyrrole polymer are formed through controlling the solvent quality, as evidenced by spectroscopic, structural, thermal and charge transport studies. Compared to beta(1), the beta(2) polymorph exhibits a lower optical band gap, an enhanced photoluminescence, a reduced pi-stacking distance, a higher hole mobility in field-effect transistors and improved photocurrent generation in polymer solar cells. The beta(1) and beta(2) polymorphs provide insights into the control of polymer self-organization for plastic electronics and hold potential for developing programmable ink formulations for next-generation electronic devices. ; This project has received funding from the European Union's Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement No. 747422, from the Netherlands Organisation for Scientific Research(016.Veni.192.106), from the Chinese Academy of Sciences (Grant No. XDB12020200), and from King Abdullah University of Science and Technology (KAUST). The research also received funding from the European Community's Seventh Framework Programme (FP7/2007-2013) (Grant Agreement no. 607585, project OSNIRO), the European Research Council (ERC Grant Agreement No. 33903), and the Ministry of Education, Culture, and Science (Gravity program 024.001.035). T.M. acknowledges the Foundation for Polish Science co-financed by the European Union under the European Regional Development Fund (First TEAM/2017-3/26). The authors acknowledge Beamline 9 of the DELTA electron storage ring in Dortmund for GIWAXS measurements. The authors thank Mateusz Brzezinski for the discussion about GIWAXS analysis, and Christ Weijtens for UPS measurements.

The interconnection layer (ICL) that connects adjacent subcells electrically and optically in solution-processed multi-junction polymer solar cells must meet functional requirements in terms of work functions, conductivity, and transparency, but also be compatible with the multiple layer stack in terms of processing and deposition conditions. Using a combination of poly(3,4-ethylenedioxythiophene):polystyrene sulfonate, diluted in near azeotropic water/n-propanol dispersions as hole transport layer, and ZnO nanoparticles, dispersed in isoamyl alcohol as electron transport layer, a novel, versatile ICL has been developed for solution-processed tandem and triple-junction solar cells in an n-i-p architecture. The ICL has been incorporated in six different tandem cells and three different triple-junction solar cells, employing a range of different polymer-fullerene photoactive layers. The new ICL provided an essentially lossless contact in each case, without the need of adjusting the formulations or deposition conditions. The approach permitted realizing complex devices in good yields, providing a power conversion efficiency up to 10%. ; European Community's Seventh Framework Programme (FP7) [607585]; European Research Council under the European Union's Seventh Framework Programme (FP)/ERC [339031]; Ministry of Education, Culture and Science [024.001.035]

Emerging photovoltaics (PVs) focus on a variety of applications complementing large scale electricity generation. Organic, dye-sensitized, and some perovskite solar cells are considered in building integration, greenhouses, wearable, and indoor applications, thereby motivating research on flexible, transparent, semitransparent, and multi-junction PVs. Nevertheless, it can be very time consuming to find or develop an up-to-date overview of the state-of-the-art performance for these systems and applications. Two important resources for recording research cells efficiencies are the National Renewable Energy Laboratory chart and the efficiency tables compiled biannually by Martin Green and colleagues. Both publications provide an effective coverage over the established technologies, bridging research and industry. An alternative approach is proposed here summarizing the best reports in the diverse research subjects for emerging PVs. Best performance parameters are provided as a function of the photovoltaic bandgap energy for each technology and application, and are put into perspective using, e.g., the Shockley–Queisser limit. In all cases, the reported data correspond to published and/or properly described certified results, with enough details provided for prospective data reproduction. Additionally, the stability test energy yield is included as an analysis parameter among state-of-the-art emerging PVs. ; O.A. acknowledges the financial support from the VDI/VD Innovation + Technik GmbH (Project-title: PV-ZUM) and the SAOT funded by the German Research Foundation (DFG) in the framework of the German excellence initiative. C.J.B. acknowledges funding from DFG within INST 90/917-1 FUGG, the SFB 953 (DFG, project no. 182849149) and the IGK 2495 (Energy Conversion Systems—from Materials to Devices). C.J.B. further acknowledges the grants "ELF-PV—Design and development of solution processed functional materials for the next generations of PV technologies" (No. 44-6521a/20/4) and "Solar Factory of the Future" (FKZ 20.2-3410.5-4-5) and the SolTech Initiative by the Bavarian State Government. A.F.N. acknowledges support from FAPESP (Grant 2017/11986-5), Shell and the strategic importance of the support given by ANP (Brazil's National Oil, Natural Gas and Biofuels Agency) through the R&D levy regulation. R.R.L. gratefully acknowledges support from the National Science Foundation under grant CBET-1702591. N.K. acknowledges funding by the US Department of Energy, Office of Energy Efficiency and Renewable Energy, Solar Energy Technologies Office, Agreement Number 34351. J.N. thanks the European Research Council for support under the European Union's Horizon 2020 research and innovation program (grant agreement No 742708).