@article{ChenSavateevPronkinetal.2017,
  author    = {Chen, Zupeng and Savateev, Aleksandr and Pronkin, Sergey and Papaefthimiou, Vasiliki and Wolff, Christian Michael and Willinger, Marc Georg and Willinger, Elena and Neher, Dieter and Antonietti, Markus and Dontsova, Dariya},
  title     = {"The Easier the Better" Preparation of Efficient Photocatalysts-Metastable Poly(heptazine imide) Salts},
  series = {Advanced materials},
  volume    = {29},
  journal   = {Advanced materials},
  publisher = {Wiley-VCH},
  address   = {Weinheim},
  issn      = {0935-9648},
  doi       = {10.1002/adma.201700555},
  pages     = {21800 -- 21806},
  year      = {2017},
  abstract  = {Cost-efficient, visible-light-driven hydrogen production from water is an attractive potential source of clean, sustainable fuel. Here, it is shown that thermal solid state reactions of traditional carbon nitride precursors (cyanamide, melamine) with NaCl, KCl, or CsCl are a cheap and straightforward way to prepare poly(heptazine imide) alkali metal salts, whose thermodynamic stability decreases upon the increase of the metal atom size. The chemical structure of the prepared salts is confirmed by the results of X-ray photoelectron and infrared spectroscopies, powder X-ray diffraction and electron microscopy studies, and, in the case of sodium poly(heptazine imide), additionally by atomic pair distribution function analysis and 2D powder X-ray diffraction pattern simulations. In contrast, reactions with LiCl yield thermodynamically stable poly(triazine imides). Owing to the metastability and high structural order, the obtained heptazine imide salts are found to be highly active photo-catalysts in Rhodamine B and 4-chlorophenol degradation, and Pt-assisted sacrificial water reduction reactions under visible light irradiation. The measured hydrogen evolution rates are up to four times higher than those provided by a benchmark photocatalyst, mesoporous graphitic carbon nitride. Moreover, the products are able to photocatalytically reduce water with considerable reaction rates, even when glycerol is used as a sacrificial hole scavenger.},
  language  = {en}
}
@article{SchulzeBettBivouretal.2020,
  author    = {Schulze, Patricia S. C. and Bett, Alexander J. and Bivour, Martin and Caprioglio, Pietro and Gerspacher, Fabian M. and Kabakl{\i}, {\"O}zde Ş. and Richter, Armin and Stolterfoht, Martin and Zhang, Qinxin and Neher, Dieter and Hermle, Martin and Hillebrecht, Harald and Glunz, Stefan W. and Goldschmidt, Jan Christoph},
  title     = {25.1\% high-efficiency monolithic perovskite silicon tandem solar cell with a high bandgap perovskite absorber},
  series = {Solar RRL},
  volume    = {4},
  journal   = {Solar RRL},
  number    = {7},
  publisher = {John Wiley \& Sons, Inc.},
  address   = {New Jersey},
  pages     = {10},
  year      = {2020},
  abstract  = {Monolithic perovskite silicon tandem solar cells can overcome the theoretical efficiency limit of silicon solar cells. This requires an optimum bandgap, high quantum efficiency, and high stability of the perovskite. Herein, a silicon heterojunction bottom cell is combined with a perovskite top cell, with an optimum bandgap of 1.68 eV in planar p-i-n tandem configuration. A methylammonium-free FA(0.75)Cs(0.25)Pb(I0.8Br0.2)(3) perovskite with high Cs content is investigated for improved stability. A 10\% molarity increase to 1.1 m of the perovskite precursor solution results in approximate to 75 nm thicker absorber layers and 0.7 mA cm(-2) higher short-circuit current density. With the optimized absorber, tandem devices reach a high fill factor of 80\% and up to 25.1\% certified efficiency. The unencapsulated tandem device shows an efficiency improvement of 2.3\% (absolute) over 5 months, showing the robustness of the absorber against degradation. Moreover, a photoluminescence quantum yield analysis reveals that with adapted charge transport materials and surface passivation, along with improved antireflection measures, the high bandgap perovskite absorber has the potential for 30\% tandem efficiency in the near future.},
  language  = {en}
}
@misc{SchulzeBettBivouretal.2020,
  author    = {Schulze, Patricia S. C. and Bett, Alexander J. and Bivour, Martin and Caprioglio, Pietro and Gerspacher, Fabian M. and Kabakl{\i}, {\"O}zde Ş. and Richter, Armin and Stolterfoht, Martin and Zhang, Qinxin and Neher, Dieter and Hermle, Martin and Hillebrecht, Harald and Glunz, Stefan W. and Goldschmidt, Jan Christoph},
  title     = {25.1\% high-efficiency monolithic perovskite silicon tandem solar cell with a high bandgap perovskite absorber},
  series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  journal   = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  number    = {7},
  issn      = {1866-8372},
  doi       = {10.25932/publishup-52566},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-525668},
  pages     = {12},
  year      = {2020},
  abstract  = {Monolithic perovskite silicon tandem solar cells can overcome the theoretical efficiency limit of silicon solar cells. This requires an optimum bandgap, high quantum efficiency, and high stability of the perovskite. Herein, a silicon heterojunction bottom cell is combined with a perovskite top cell, with an optimum bandgap of 1.68 eV in planar p-i-n tandem configuration. A methylammonium-free FA(0.75)Cs(0.25)Pb(I0.8Br0.2)(3) perovskite with high Cs content is investigated for improved stability. A 10\% molarity increase to 1.1 m of the perovskite precursor solution results in approximate to 75 nm thicker absorber layers and 0.7 mA cm(-2) higher short-circuit current density. With the optimized absorber, tandem devices reach a high fill factor of 80\% and up to 25.1\% certified efficiency. The unencapsulated tandem device shows an efficiency improvement of 2.3\% (absolute) over 5 months, showing the robustness of the absorber against degradation. Moreover, a photoluminescence quantum yield analysis reveals that with adapted charge transport materials and surface passivation, along with improved antireflection measures, the high bandgap perovskite absorber has the potential for 30\% tandem efficiency in the near future.},
  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}
}
@article{KietzkeNeherKumkeetal.2004,
  author    = {Kietzke, Thomas and Neher, Dieter and Kumke, Michael Uwe and Montenegro, Rivelino V. D. and Landfester, Katharina and Scherf, Ullrich},
  title     = {A nanoparticle approach to control the phase separation in polyfluorene photovoltaic devices},
  year      = {2004},
  abstract  = {Polymer solar cell devices with nanostructured blend layers have been fabricated using single- and dual- component polymer nanospheres. Starting from an electron-donating and an electron-accepting polyfluorene derivative, PFB and F8BT, dissolved in suitable organic solvents, dispersions of solid particles with mean diameters of ca. 50 nm, containing either the pure polymer components or a mixture of PFB and F8BT in each particle, were prepared with the miniemulsion process. Photovoltaic devices based on these particles have been studied with respect to the correlation between external quantum efficiency and layer composition. It is shown that the properties of devices containing a blend of single-component PFB and F8BT particles differ significantly from those of solar cells based on blend particles, even for the same layer composition. Various factors determining the quantum efficiency in both kinds of devices are identified and discussed, taking into account the spectroscopic properties of the particles. An external quantum efficiency of ca. 4\% is measured for a device made from polymer blend nanoparticles containing PFB:F8BT at a weight ratio of 1:2 in each individual nanosphere. This is among the highest values reported so far for photovoltaic cells using this material combination},
  language  = {en}
}
@article{NeherKniepertElimelechetal.2016,
  author    = {Neher, Dieter and Kniepert, Juliane and Elimelech, Arik and Koster, L. Jan Anton},
  title     = {A New Figure of Merit for Organic Solar Cells with Transport-limited Photocurrents},
  series = {Scientific reports},
  volume    = {6},
  journal   = {Scientific reports},
  publisher = {Nature Publishing Group},
  address   = {London},
  issn      = {2045-2322},
  doi       = {10.1038/srep24861},
  pages     = {9},
  year      = {2016},
  abstract  = {Compared to their inorganic counterparts, organic semiconductors suffer from relatively low charge carrier mobilities. Therefore, expressions derived for inorganic solar cells to correlate characteristic performance parameters to material properties are prone to fail when applied to organic devices. This is especially true for the classical Shockley-equation commonly used to describe current-voltage (JV)-curves, as it assumes a high electrical conductivity of the charge transporting material. Here, an analytical expression for the JV-curves of organic solar cells is derived based on a previously published analytical model. This expression, bearing a similar functional dependence as the Shockley-equation, delivers a new figure of merit α to express the balance between free charge recombination and extraction in low mobility photoactive materials. This figure of merit is shown to determine critical device parameters such as the apparent series resistance and the fill factor.},
  language  = {en}
}
@misc{NeherKniepertElimelechetal.2016,
  author    = {Neher, Dieter and Kniepert, Juliane and Elimelech, Arik and Koster, L. Jan Anton},
  title     = {A New Figure of Merit for Organic Solar Cells with Transport-limited Photocurrents},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-91414},
  pages     = {9},
  year      = {2016},
  abstract  = {Compared to their inorganic counterparts, organic semiconductors suffer from relatively low charge carrier mobilities. Therefore, expressions derived for inorganic solar cells to correlate characteristic performance parameters to material properties are prone to fail when applied to organic devices. This is especially true for the classical Shockley-equation commonly used to describe current-voltage (JV)-curves, as it assumes a high electrical conductivity of the charge transporting material. Here, an analytical expression for the JV-curves of organic solar cells is derived based on a previously published analytical model. This expression, bearing a similar functional dependence as the Shockley-equation, delivers a new figure of merit α to express the balance between free charge recombination and extraction in low mobility photoactive materials. This figure of merit is shown to determine critical device parameters such as the apparent series resistance and the fill factor.},
  language  = {en}
}
@article{NeherKniepertElimelechetal.2016,
  author    = {Neher, Dieter and Kniepert, Juliane and Elimelech, Arik and Koster, L. Jan Anton},
  title     = {A New Figure of Merit for Organic Solar Cells with Transport-limited Photocurrents},
  series = {Scientific reports},
  volume    = {6},
  journal   = {Scientific reports},
  publisher = {Nature Publ. Group},
  address   = {London},
  issn      = {2045-2322},
  doi       = {10.1038/srep24861},
  pages     = {E2348 -- E2349},
  year      = {2016},
  abstract  = {Compared to their inorganic counterparts, organic semiconductors suffer from relatively low charge carrier mobilities. Therefore, expressions derived for inorganic solar cells to correlate characteristic performance parameters to material properties are prone to fail when applied to organic devices. This is especially true for the classical Shockley-equation commonly used to describe current-voltage (JV)-curves, as it assumes a high electrical conductivity of the charge transporting material. Here, an analytical expression for the JV-curves of organic solar cells is derived based on a previously published analytical model. This expression, bearing a similar functional dependence as the Shockley-equation, delivers a new figure of merit a to express the balance between free charge recombination and extraction in low mobility photoactive materials. This figure of merit is shown to determine critical device parameters such as the apparent series resistance and the fill factor.},
  language  = {en}
}
@misc{InalKoelschSellrieetal.2013,
  author    = {Inal, Sahika and K{\"o}lsch, Jonas D. and Sellrie, Frank and Schenk, J{\"o}rg A. and Wischerhoff, Erik and Laschewsky, Andr{\´e} and Neher, Dieter},
  title     = {A water soluble fluorescent polymer as a dual colour sensor for temperature and a specific protein},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-95336},
  pages     = {6373 -- 6381},
  year      = {2013},
  abstract  = {We present two thermoresponsive water soluble copolymers prepared via free radical statistical copolymerization of N-isopropylacrylamide (NIPAm) and of oligo(ethylene glycol) methacrylates (OEGMAs), respectively, with a solvatochromic 7-(diethylamino)-3-carboxy-coumarin (DEAC)- functionalized monomer. In aqueous solutions, the NIPAm-based copolymer exhibits characteristic changes in its fluorescence profile in response to a change in solution temperature as well as to the presence of a specific protein, namely an anti-DEAC antibody. This polymer emits only weakly at low temperatures, but exhibits a marked fluorescence enhancement accompanied by a change in its emission colour when heated above its cloud point. Such drastic changes in the fluorescence and absorbance spectra are observed also upon injection of the anti-DEAC antibody, attributed to the specific binding of the antibody to DEAC moieties. Importantly, protein binding occurs exclusively when the polymer is in the well hydrated state below the cloud point, enabling a temperature control on the molecular recognition event. On the other hand, heating of the polymer-antibody complexes releases a fraction of the bound antibody. In the presence of the DEAC-functionalized monomer in this mixture, the released antibody competitively binds to the monomer and the antibody-free chains of the polymer undergo a more effective collapse and inter-aggregation. In contrast, the emission properties of the OEGMA-based analogous copolymer are rather insensitive to the thermally induced phase transition or to antibody binding. These opposite behaviours underline the need for a carefully tailored molecular design of responsive polymers aimed at specific applications, such as biosensing.},
  language  = {en}
}
@article{InalKoelschSellrieetal.2013,
  author    = {Inal, Sahika and K{\"o}lsch, Jonas D. and Sellrie, Frank and Schenk, J{\"o}rg A. and Wischerhoff, Erik and Laschewsky, Andr{\´e} and Neher, Dieter},
  title     = {A water soluble fluorescent polymer as a dual colour sensor for temperature and a specific protein},
  series = {Journal of materials chemistry : B, Materials for biology and medicine},
  volume    = {1},
  journal   = {Journal of materials chemistry : B, Materials for biology and medicine},
  number    = {46},
  publisher = {Royal Society of Chemistry},
  address   = {Cambridge},
  issn      = {2050-750X},
  doi       = {10.1039/c3tb21245a},
  pages     = {6373 -- 6381},
  year      = {2013},
  abstract  = {We present two thermoresponsive water soluble copolymers prepared via free radical statistical copolymerization of N-isopropylacrylamide (NIPAm) and of oligo(ethylene glycol) methacrylates (OEGMAs), respectively, with a solvatochromic 7-(diethylamino)-3-carboxy-coumarin (DEAC)-functionalized monomer. In aqueous solutions, the NIPAm-based copolymer exhibits characteristic changes in its fluorescence profile in response to a change in solution temperature as well as to the presence of a specific protein, namely an anti-DEAC antibody. This polymer emits only weakly at low temperatures, but exhibits a marked fluorescence enhancement accompanied by a change in its emission colour when heated above its cloud point. Such drastic changes in the fluorescence and absorbance spectra are observed also upon injection of the anti-DEAC antibody, attributed to the specific binding of the antibody to DEAC moieties. Importantly, protein binding occurs exclusively when the polymer is in the well hydrated state below the cloud point, enabling a temperature control on the molecular recognition event. On the other hand, heating of the polymer-antibody complexes releases a fraction of the bound antibody. In the presence of the DEAC-functionalized monomer in this mixture, the released antibody competitively binds to the monomer and the antibody-free chains of the polymer undergo a more effective collapse and inter-aggregation. In contrast, the emission properties of the OEGMA-based analogous copolymer are rather insensitive to the thermally induced phase transition or to antibody binding. These opposite behaviours underline the need for a carefully tailored molecular design of responsive polymers aimed at specific applications, such as biosensing.},
  language  = {en}
}