@article{VandewalAlbrechtHokeetal.2014,
  author    = {Vandewal, Koen and Albrecht, Steve and Hoke, Eric T. and Graham, Kenneth R. and Widmer, Johannes and Douglas, Jessica D. and Schubert, Marcel and Mateker, William R. and Bloking, Jason T. and Burkhard, George F. and Sellinger, Alan and Frechet, Jean M. J. and Amassian, Aram and Riede, Moritz K. and McGehee, Michael D. and Neher, Dieter and Salleo, Alberto},
  title     = {Efficient charge generation by relaxed charge-transfer states at organic interfaces},
  series = {Nature materials},
  volume    = {13},
  journal   = {Nature materials},
  number    = {1},
  publisher = {Nature Publ. Group},
  address   = {London},
  issn      = {1476-1122},
  doi       = {10.1038/NMAT3807},
  pages     = {63 -- 68},
  year      = {2014},
  abstract  = {carriers on illumination. Efficient organic solar cells require a high yield for this process, combined with a minimum of energy losses. Here, we investigate the role of the lowest energy emissive interfacial charge-transfer state (CT1) in the charge generation process. We measure the quantum yield and the electric field dependence of charge generation on excitation of the charge-transfer (CT) state manifold viaweakly allowed, low-energy optical transitions. For a wide range of photovoltaic devices based on polymer: fullerene, small-molecule:C-60 and polymer: polymer blends, our study reveals that the internal quantum efficiency (IQE) is essentially independent of whether or not D, A or CT states with an energy higher than that of CT1 are excited. The best materials systems show an IQE higher than 90\% without the need for excess electronic or vibrational energy.},
  language  = {en}
}
@article{LiuTkachovKomberetal.2014,
  author    = {Liu, W. and Tkachov, R. and Komber, H. and Senkovskyy, V. and Schubert, M. and Wei, Z. and Facchetti, A. and Neher, Dieter and Kiriy, A.},
  title     = {Chain-growth polycondensation of perylene diimide-based copolymers: a new route to regio-regular perylene diimide-based acceptors for all-polymer solar cells and n-type transistors},
  series = {Polymer Chemistry},
  volume    = {5},
  journal   = {Polymer Chemistry},
  number    = {10},
  publisher = {Royal Society of Chemistry},
  address   = {Cambridge},
  issn      = {1759-9954},
  doi       = {10.1039/c3py01707a},
  pages     = {3404 -- 3411},
  year      = {2014},
  abstract  = {Herein, we report the chain-growth tin-free room temperature polymerization method to synthesize n-type perylene diimide-dithiophene-based conjugated polymers (PPDIT2s) suitable for solar cell and transistor applications. The palladium/electron-rich tri-tert-butylphosphine catalyst is effective to enable the chain-growth polymerization of anion-radical monomer Br-TPDIT-Br/Zn to PPDIT2 with a molecular weight up to M-w approximate to 50 kg mol(-1) and moderate polydispersity. This is the second example of the polymerization of unusual anion-radical aromatic complexes formed in a reaction of active Zn and electron-deficient diimide-based aryl halides. As such, the discovered polymerization method is not a specific reactivity feature of the naphthalene-diimide derivatives but is rather a general polymerization tool. This is an important finding, given the significantly higher maximum external quantum efficiency that can be reached with PDI-based copolymers (32-45\%) in all-polymer solar cells compared to NDI-based materials (15-30\%). Our studies revealed that PPDIT2 synthesized by the new method and the previously published polymer prepared by step-growth Stille polycondensation show similar electron mobility and all-polymer solar cell performance. At the same time, the polymerization reported herein has several technological advantages as it proceeds relatively fast at room temperature and does not involve toxic tin-based compounds. Because several chain-growth polymerization reactions are well-suited for the preparation of well-defined multi-functional polymer architectures, the next target is to explore the utility of the discovered polymerization in the synthesis of end-functionalized polymers and block copolymers. Such materials would be helpful to improve the nanoscale morphology of polymer blends in all-polymer solar cells.},
  language  = {en}
}
@misc{MouleNeherTurner2014,
  author    = {Moule, Adam J. and Neher, Dieter and Turner, Sarah T.},
  title     = {P3HT-Based solar cells: structural properties and photovoltaic performance},
  series = {Advances in Polymer Science},
  volume    = {265},
  journal   = {Advances in Polymer Science},
  editor    = {Ludwigs, S},
  publisher = {Springer},
  address   = {Berlin},
  isbn      = {978-3-662-45145-8; 978-3-662-45144-1},
  issn      = {0065-3195},
  doi       = {10.1007/12_2014_289},
  pages     = {181 -- 232},
  year      = {2014},
  abstract  = {Each year we are bombarded with B.Sc. and Ph.D. applications from students that want to improve the world. They have learned that their future depends on changing the type of fuel we use and that solar energy is our future. The hope and energy of these young people will transform future energy technologies, but it will not happen quickly. Organic photovoltaic devices are easy to sketch, but the materials, processing steps, and ways of measuring the properties of the materials are very complicated. It is not trivial to make a systematic measurement that will change the way other research groups think or practice. In approaching this chapter, we thought about what a new researcher would need to know about organic photovoltaic devices and materials in order to have a good start in the subject. Then, we simplified that to focus on what a new researcher would need to know about poly-3-hexylthiophene: phenyl-C61-butyric acid methyl ester blends (P3HT: PCBM) to make research progress with these materials. This chapter is by no means authoritative or a compendium of all things on P3HT: PCBM. We have selected to explain how the sample fabrication techniques lead to control of morphology and structural features and how these morphological features have specific optical and electronic consequences for organic photovoltaic device applications.},
  language  = {en}
}
@article{FoertigKniepertGlueckeretal.2014,
  author    = {Foertig, Alexander and Kniepert, Juliane and Gluecker, Markus and Brenner, Thomas J. K. and Dyakonov, Vladimir and Neher, Dieter and Deibel, Carsten},
  title     = {Nongeminate and geminate recombination in PTB7: PCBM solar cells},
  series = {Advanced functional materials},
  volume    = {24},
  journal   = {Advanced functional materials},
  number    = {9},
  publisher = {Wiley-VCH},
  address   = {Weinheim},
  issn      = {1616-301X},
  doi       = {10.1002/adfm.201302134},
  pages     = {1306 -- 1311},
  year      = {2014},
  language  = {en}
}
@article{SteyrleuthnerDiPietroCollinsetal.2014,
  author    = {Steyrleuthner, Robert and Di Pietro, Riccardo and Collins, Brian A. and Polzer, Frank and Himmelberger, Scott and Schubert, Marcel and Chen, Zhihua and Zhang, Shiming and Salleo, Alberto and Ade, Harald W. and Facchetti, Antonio and Neher, Dieter},
  title     = {The Role of Regioregularity, Crystallinity, and Chain Orientation on Electron Transport in a High-Mobility n-Type Copolymer},
  series = {Journal of the American Chemical Society},
  volume    = {136},
  journal   = {Journal of the American Chemical Society},
  number    = {11},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {0002-7863},
  doi       = {10.1021/ja4118736},
  pages     = {4245 -- 4256},
  year      = {2014},
  language  = {en}
}
@article{AlbrechtVandewalTumblestonetal.2014,
  author    = {Albrecht, Steve and Vandewal, Koen and Tumbleston, John R. and Fischer, Florian S. U. and Douglas, Jessica D. and Frechet, Jean M. J. and Ludwigs, Sabine and Ade, Harald W. and Salleo, Alberto and Neher, Dieter},
  title     = {On the efficiency of charge transfer state splitting in polymer: Fullerene solar cells},
  series = {Advanced materials},
  volume    = {26},
  journal   = {Advanced materials},
  number    = {16},
  publisher = {Wiley-VCH},
  address   = {Weinheim},
  issn      = {0935-9648},
  doi       = {10.1002/adma.201305283},
  pages     = {2533 -- 2539},
  year      = {2014},
  language  = {en}
}
@article{AlbrechtTumblestonJanietzetal.2014,
  author    = {Albrecht, Steve and Tumbleston, John R. and Janietz, Silvia and Dumsch, Ines and Allard, Sybille and Scherf, Ullrich and Ade, Harald W. and Neher, Dieter},
  title     = {Quantifying charge extraction in organic solar cells: The case of fluorinated PCPDTBT},
  series = {The journal of physical chemistry letters},
  volume    = {5},
  journal   = {The journal of physical chemistry letters},
  number    = {7},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {1948-7185},
  doi       = {10.1021/jz500457b},
  pages     = {1131 -- 1138},
  year      = {2014},
  abstract  = {We introduce a new and simple method to quantify the effective extraction mobility in organic solar cells at low electric fields and charge carrier densities comparable to operation conditions under one sun illumination. By comparing steady-state carrier densities at constant illumination intensity and under open-circuit conditions, the gradient of the quasi-Fermi potential driving the current is estimated as a function of external bias and charge density. These properties are then related to the respective steady-state current to determine the effective extraction mobility. The new technique is applied to different derivatives of the well-known low-band-gap polymer PCPDTBT blended with PC70BM. We show that the slower average extraction due to lower mobility accounts for the moderate fill factor when solar cells are fabricated with mono- or difluorinated PCPDTBT. This lower extraction competes with improved generation and reduced nongeminate recombination, rendering the monofluorinated derivative the most efficient donor polymer.},
  language  = {en}
}
@article{ShalomInalNeheretal.2014,
  author    = {Shalom, Menny and Inal, Sahika and Neher, Dieter and Antonietti, Markus},
  title     = {SiO2/carbon nitride composite materials: The role of surfaces for enhanced photocatalysis},
  series = {Catalysis today : a serial publication dealing with topical themes in catalysis and related subjects},
  volume    = {225},
  journal   = {Catalysis today : a serial publication dealing with topical themes in catalysis and related subjects},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {0920-5861},
  doi       = {10.1016/j.cattod.2013.12.013},
  pages     = {185 -- 190},
  year      = {2014},
  abstract  = {The effect of SiO2 nanoparticles on carbon nitride (C3N4) photoactivity performance is described. The composite SiO2-C3N4 materials exhibit a higher activity in the photo degradation of RhB dye. A detailed analysis of the chemical and optical properties of the composite C3N4 materials shows that the photo activity increases with higher SiO2 concentration. We found out that the presence of SiO2 nanoparticles strongly affects the fluorescence intensity of the matrix and life time by the creation of new energy states for charge transfer within the C3N4. Furthermore, the use of SiO2 in the synthesis of C3N4 leads to new morphology with higher surface area which results in another, secondary improvement of C3N4 photoactivity. The effect of different surfaces within C3N4 on its chemical and electronic properties is discussed and a tentative mechanism is proposed. The utilization of SiO2 nanoparticles improves both photophysical and chemical properties of C3N4 and opens new possibilities for further enhancement of C3N4 catalytic properties by the formation of composites with many other materials.},
  language  = {en}
}
@article{PradhanAlbrechtStilleretal.2014,
  author    = {Pradhan, Basudev and Albrecht, Steve and Stiller, Burkhard and Neher, Dieter},
  title     = {Inverted organic solar cells comprising low-temperature-processed ZnO films},
  series = {Applied physics : A, Materials science \& processing},
  volume    = {115},
  journal   = {Applied physics : A, Materials science \& processing},
  number    = {2},
  publisher = {Springer},
  address   = {New York},
  issn      = {0947-8396},
  doi       = {10.1007/s00339-014-8373-8},
  pages     = {365 -- 369},
  year      = {2014},
  abstract  = {Inverted organic solar cells are fabricated using low-temperature-annealed ZnO film as an electron transport layer. Uniform ZnO films were prepared by spin coating a diethylzinc (DEZ) precursor solution in air, followed by annealing at 100 A degrees C. Organic solar cells prepared on these ZnO films with a 1:1 P3HT:PCBM blend as the active layer show a high power conversion efficiency of 4.03 \%, which is more than 10 \% higher than the PCE of solar cells comprising ZnO prepared via a high-temperature sol-gel route.},
  language  = {en}
}
@article{KniepertLangevanderKaapetal.2014,
  author    = {Kniepert, Juliane and Lange, Ilja and van der Kaap, Niels J. and Koster, L. Jan Anton and Neher, Dieter},
  title     = {A conclusive view on charge generation, recombination, and extraction in As-prepared and annealed P3HT:PCBM blends: combined experimental and simulation work},
  series = {dvanced energy materials},
  volume    = {4},
  journal   = {dvanced energy materials},
  number    = {7},
  publisher = {Wiley-VCH},
  address   = {Weinheim},
  issn      = {1614-6832},
  doi       = {10.1002/aenm.201301401},
  pages     = {11},
  year      = {2014},
  abstract  = {Time-delayed collection field (TDCF) and bias-amplified charge extraction (BACE) are applied to as-prepared and annealed poly(3-hexylthiophene):[6,6]-phenyl C-71 butyric acid methyl ester (P3HT:PCBM) blends coated from chloroform. Despite large differences in fill factor, short-circuit current, and power conversion efficiency, both blends exhibit a negligible dependence of photogeneration on the electric field and strictly bimolecular recombination (BMR) with a weak dependence of the BMR coefficient on charge density. Drift-diffusion simulations are performed using the measured coefficients and mobilities, taking into account bimolecular recombination and the possible effects of surface recombination. The excellent agreement between the simulation and the experimental data for an intensity range covering two orders of magnitude indicates that a field-independent generation rate and a density-independent recombination coefficient describe the current-voltage characteristics of the annealed P3HT: PCBM devices, while the performance of the as-prepared blend is shown to be limited by space charge effects due to a low hole mobility. Finally, even though the bimolecular recombination coefficient is small, surface recombination is found to be a negligible loss mechanism in these solar cells.},
  language  = {en}
}