TY - GEN A1 - Stolterfoht, Martin A1 - Grischek, Max A1 - Caprioglio, Pietro A1 - Wolff, Christian Michael A1 - Gutierrez-Partida, Emilio A1 - Peña-Camargo, Francisco A1 - Rothhardt, Daniel A1 - Zhang, Shanshan A1 - Raoufi, Meysam A1 - Wolansky, Jakob A1 - Abdi-Jalebi, Mojtaba A1 - Stranks, Samuel D. A1 - Albrecht, Steve A1 - Kirchartz, Thomas A1 - Neher, Dieter T1 - How to quantify the efficiency potential of neat perovskite films BT - Perovskite semiconductors with an implied efficiency exceeding 28% T2 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - Perovskite photovoltaic (PV) cells have demonstrated power conversion efficiencies (PCE) that are close to those of monocrystalline silicon cells; however, in contrast to silicon PV, perovskites are not limited by Auger recombination under 1-sun illumination. Nevertheless, compared to GaAs and monocrystalline silicon PV, perovskite cells have significantly lower fill factors due to a combination of resistive and non-radiative recombination losses. This necessitates a deeper understanding of the underlying loss mechanisms and in particular the ideality factor of the cell. By measuring the intensity dependence of the external open-circuit voltage and the internal quasi-Fermi level splitting (QFLS), the transport resistance-free efficiency of the complete cell as well as the efficiency potential of any neat perovskite film with or without attached transport layers are quantified. Moreover, intensity-dependent QFLS measurements on different perovskite compositions allows for disentangling of the impact of the interfaces and the perovskite surface on the non-radiative fill factor and open-circuit voltage loss. It is found that potassium-passivated triple cation perovskite films stand out by their exceptionally high implied PCEs > 28%, which could be achieved with ideal transport layers. Finally, strategies are presented to reduce both the ideality factor and transport losses to push the efficiency to the thermodynamic limit. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1434 KW - non-radiative interface recombination KW - perovskite solar cells KW - photoluminescence Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-516622 SN - 1866-8372 IS - 17 ER - TY - JOUR A1 - Stolterfoht, Martin A1 - Grischek, Max A1 - Caprioglio, Pietro A1 - Wolff, Christian Michael A1 - Gutierrez-Partida, Emilio A1 - Peña-Camargo, Francisco A1 - Rothhardt, Daniel A1 - Zhang, Shanshan A1 - Raoufi, Meysam A1 - Wolansky, Jakob A1 - Abdi-Jalebi, Mojtaba A1 - Stranks, Samuel D. A1 - Albrecht, Steve A1 - Kirchartz, Thomas A1 - Neher, Dieter T1 - How to quantify the efficiency potential of neat perovskite films BT - Perovskite semiconductors with an implied efficiency exceeding 28% JF - Advanced Materials N2 - Perovskite photovoltaic (PV) cells have demonstrated power conversion efficiencies (PCE) that are close to those of monocrystalline silicon cells; however, in contrast to silicon PV, perovskites are not limited by Auger recombination under 1-sun illumination. Nevertheless, compared to GaAs and monocrystalline silicon PV, perovskite cells have significantly lower fill factors due to a combination of resistive and non-radiative recombination losses. This necessitates a deeper understanding of the underlying loss mechanisms and in particular the ideality factor of the cell. By measuring the intensity dependence of the external open-circuit voltage and the internal quasi-Fermi level splitting (QFLS), the transport resistance-free efficiency of the complete cell as well as the efficiency potential of any neat perovskite film with or without attached transport layers are quantified. Moreover, intensity-dependent QFLS measurements on different perovskite compositions allows for disentangling of the impact of the interfaces and the perovskite surface on the non-radiative fill factor and open-circuit voltage loss. It is found that potassium-passivated triple cation perovskite films stand out by their exceptionally high implied PCEs > 28%, which could be achieved with ideal transport layers. Finally, strategies are presented to reduce both the ideality factor and transport losses to push the efficiency to the thermodynamic limit. KW - non-radiative interface recombination KW - perovskite solar cells KW - photoluminescence Y1 - 2020 U6 - https://doi.org/10.1002/adma.202000080 SN - 0935-9648 SN - 1521-4095 VL - 32 IS - 17 SP - 1 EP - 10 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Chen, Zupeng A1 - Savateev, Aleksandr A1 - Pronkin, Sergey A1 - Papaefthimiou, Vasiliki A1 - Wolff, Christian Michael A1 - Willinger, Marc Georg A1 - Willinger, Elena A1 - Neher, Dieter A1 - Antonietti, Markus A1 - Dontsova, Dariya T1 - "The Easier the Better" Preparation of Efficient Photocatalysts-Metastable Poly(heptazine imide) Salts JF - Advanced materials N2 - 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. KW - carbon nitride KW - glycerol oxidation KW - mesocrystals KW - poly(heptazine imide) KW - water reduction reactions Y1 - 2017 U6 - https://doi.org/10.1002/adma.201700555 SN - 0935-9648 SN - 1521-4095 VL - 29 SP - 21800 EP - 21806 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Inal, Sahika A1 - Kölsch, Jonas D. A1 - Sellrie, Frank A1 - Schenk, Jörg A. A1 - Wischerhoff, Erik A1 - Laschewsky, André A1 - Neher, Dieter T1 - A water soluble fluorescent polymer as a dual colour sensor for temperature and a specific protein JF - Journal of materials chemistry : B, Materials for biology and medicine N2 - 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. Y1 - 2013 U6 - https://doi.org/10.1039/c3tb21245a SN - 2050-750X SN - 2050-7518 VL - 1 IS - 46 SP - 6373 EP - 6381 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Shalom, Menny A1 - Inal, Sahika A1 - Neher, Dieter A1 - Antonietti, Markus T1 - SiO2/carbon nitride composite materials: The role of surfaces for enhanced photocatalysis JF - Catalysis today : a serial publication dealing with topical themes in catalysis and related subjects N2 - 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. KW - Carbon nitride KW - SiO2 composite material KW - Photocatalysis KW - RhB degradation Y1 - 2014 U6 - https://doi.org/10.1016/j.cattod.2013.12.013 SN - 0920-5861 SN - 1873-4308 VL - 225 SP - 185 EP - 190 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Landfester, Katharina A1 - Montenegro, Rivelino V. D. A1 - Scherf, Ullrich A1 - Günter, R. A1 - Asawapirom, Udom A1 - Patil, S. A1 - Neher, Dieter A1 - Kietzke, Thomas T1 - Semiconducting polymer nanospheres in aqeous dispersion prepared by a miniemulsion process Y1 - 2002 ER - TY - GEN A1 - Wolff, Christian Michael A1 - Canil, Laura A1 - Rehermann, Carolin A1 - Nguyen, Ngoc Linh A1 - Zu, Fengshuo A1 - Ralaiarisoa, Maryline A1 - Caprioglio, Pietro A1 - Fiedler, Lukas A1 - Stolterfoht, Martin A1 - Kogikoski, Junior, Sergio A1 - Bald, Ilko A1 - Koch, Norbert A1 - Unger, Eva L. A1 - Dittrich, Thomas A1 - Abate, Antonio A1 - Neher, Dieter T1 - Correction to 'Perfluorinated self-assembled monolayers enhance the stability and efficiency of inverted perovskite solar cells' (2020, 14 (2), 1445−1456) T2 - ACS nano Y1 - 2020 U6 - https://doi.org/10.1021/acsnano.0c08081 SN - 1936-0851 SN - 1936-086X VL - 14 IS - 11 SP - 16156 EP - 16156 PB - American Chemical Society CY - Washington, DC ER - TY - JOUR A1 - Albrecht, Steve A1 - Grootoonk, Bjorn A1 - Neubert, Sebastian A1 - Roland, Steffen A1 - Wordenweber, Jan A1 - Meier, Matthias A1 - Schlatmann, Rutger A1 - Gordijn, Aad A1 - Neher, Dieter T1 - Efficient hybrid inorganic/organic tandem solar cells with tailored recombination contacts JF - Solar energy materials & solar cells : an international journal devoted to photovoltaic, photothermal, and photochemical solar energy conversion N2 - In this work, the authors present a 7.5% efficient hybrid tandem solar cell with the bottom cell made of amorphous silicon and a Si-PCPDTBT:PC70BM bulk heterojunction top cell. Loss-free recombination contacts were realized by combing Al-doped ZnO with either the conducting polymer composite PEDOT:PSS or with a bilayer of ultrathin Al and MoO3. Optimization of these contacts results in tandem cells with high fill factors of 70% and an open circuit voltage close to the sum of those of the sub-cells. This is the best efficiency reported for this type of hybrid tandem cell so far. Optical and electrical device modeling suggests that the efficiency can be increased to similar to 12% on combining a donor polymer with suitable absorption onset with PCBM. We also describe proof-of-principle studies employing light trapping in hybrid tandem solar cells, suggesting that this device architecture has the potential to achieve efficiencies well above 12%. (C) 2014 Elsevier B.V. All rights reserved. KW - Hybrid solar cells KW - Tandem solar cells KW - Organic solar cells KW - Bulk heterojunction KW - Efficiency optimization Y1 - 2014 U6 - https://doi.org/10.1016/j.solmat.2014.04.020 SN - 0927-0248 SN - 1879-3398 VL - 127 SP - 157 EP - 162 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Zen, Achmad A1 - Neher, Dieter A1 - Silmy, Kamel A1 - Hollander, A. A1 - Asawapirom, Udom A1 - Scherf, Ullrich T1 - Improving the performance of organic field effect transistor by optimizing the gate insulator surface N2 - The effect of oxygen plasma treatment and/or silanization with hexamethyldisilazane (HMDS) on the surface chemistry and the morphology of the SiO2-gate insulator were studied with respect to the performance of organic field effect transistors. Using X-ray photoelectron spectroscopy (XPS), it is shown that silanization leads to the growth of a polysiloxane interfacial layer and that longer silanization times increase the thickness of this layer. Most important, silanization reduces the signal from surface contaminations such as oxidized hydrocarbon molecules. In fact, the lowest concentration of these contaminations was found after a combined oxygen plasma/silanization treatment. The results of these investigations were correlated with the characteristic device parameters of polymer field effect transistors with poly(3-hexylthiophene)s as the semiconducting layer. We found that the field effect mobility correlates with the concentration of contaminations as measured by XPS. We, finally, demonstrate that silanization significantly improves the operational stability of the device in air compared to the untreated devices Y1 - 2005 ER - TY - JOUR A1 - Däubler, Thomas Karl A1 - Glowacki, Ireneusz A1 - Scherf, Ullrich A1 - Ulanski, J. A1 - Hörhold, Hans-Heinrich A1 - Neher, Dieter T1 - Photogeneration and transport of charge carriers in hybrid materials of conjugated polymers and dye-sensitized TiO2 Y1 - 1999 ER -